1. Essentials of Radiation Therapy
Basil Tumaini MD, MMED Resident
03 August 2018
Muhimbili University

2. Outline
Introduction
Sources of ionizing radiation
Basis for radiotherapy
Clinical uses of RT
Radiation oncology team
Treatment process
Delivery of radiotherapy
Side effects and complications of RT
Summary

3. Introduction
 Radiation therapy sometimes called:
 radiotherapy
 irradiation
 Radiotherapy is the treatment of disease using
penetrating beams of high energy waves or streams
of particles called radiation (x-rays, γ-rays, electrons,
protons, or neutrons)

4. Sources of Ionizing Radiation
 Photons
 Gamma Rays
Emitted from a nucleus of a radioactive atom
 Cobalt treatment machine
 Radioisotopes used in brachytherapy
 X-rays
 Generated by a linear accelerator when
accelerated electrons hit a target
 Particle Beams
 Protons
 Neutrons
 Electrons
Most external beam radiation
treatments use photons generated
by a linear accelerator.
Source: Varian Medical Systems
Inc.
Cherry P, Duxbury A, editors. Practical radiotherapy: physics and equipment.
John Wiley & Sons; 2009 Sep 8.

5. Biologic Basis for Radiotherapy
 Radiation therapy works by damaging the
DNA of cells and destroys their ability to
reproduce
 Both normal and cancer cells can be
affected by radiation, but cancer cells
have generally impaired ability to repair
this damage, leading to cell death
 All tissues have a tolerance level, or
maximum dose, beyond which irreparable
damage may occur
Steel GG, Adams GE, Horwich A. The biological basis of radiotherapy.1989

6.  Radiation kills cells that are actively dividing.
 It also causes damage to the surrounding
tissue.
 Radiation doesn’t kill cells instantly, it may
take day to weeks depending on the cell
 Skin, bone marrow, lining of intestines affected
quickly
 Nerve, breast, brain, and bone tissue show
affected later

7. Fractionation
Fractionation, or dividing the total dose into small
daily fractions over several weeks, takes advantage of
differential repair abilities of normal and malignant
tissues
Fractionation spares normal tissue through repair
and repopulation while increasing damage to tumor
cells through redistribution and reoxygenation
Williams MV, James ND, Summers ET, Barrett A, Ash DV, Audit Sub-Committee.
National survey of radiotherapy fractionation practice in 2003. Clinical Oncology.
2006 Feb 1;18(1):3-14.

8. Radiocurability and radiosensitivity
 RADIOCURABILITY – refers to the eradication of
tumour at the primary or regional site and reflects a
direct effect of the irradiation - but this does not
equate with patients cure from cancer
 RADIOSENSITIVITY – is the measure of tumour
radiation response, thus describing the degree and
speed of regression during and immediately after
radiotherapy
Fertil B, Malaise EP. Inherent cellular radiosensitivity as a basic concept for
human tumor radiotherapy. International Journal of Radiation Oncology•
Biology• Physics. 1981 May 1;7(5):621-9.
Gerweck LE, Zaidi ST, Zietman A. Multivariate determinants of radiocurability
I: prediction of single fraction tumor control doses. International Journal of
Radiation Oncology* Biology* Physics. 1994 Apr 30;29(1):57-66.

9. Factors affecting radiosensitivity
 Histologic type
 High sensitivity: Malignant lymphoma, Seminoma
 Moderate sensitivity: Epithelial tumour (Carcinoma)
 Low sensitivity: Osteosarcoma, Malignant melanoma
 Oxygen concentration in tumour tissue:
 Radiosensitivity is low in the hypoxic state.
 Cell cycle: Radiosensitivity is high in M phase and low
in S phase
 Cancer-related genes: p53, Bel-2, Fas, VEGF

10. The Four R’s of Radiobiology
Four major factors are believed to affect tissue’s
response to fractionated radiation:
 Repair of sublethal damage to cells caused by radiation
between fractions
 Repopulation or regrowth of cells between fractions
 Redistribution of cells into radiosensitive phases of cell
cycle
 Reoxygenation of hypoxic cells to make them more
sensitive to radiation
Withers HR. The four R's of radiotherapy. InAdvances in radiation biology 1975
Jan 1 (Vol. 5, pp. 241-271). Elsevier.

11. Clinical Uses for RT
Therapeutic radiation serves two
major functions
 To cure cancer
 Destroy tumors that have not spread
 Kill residual microscopic disease left after
surgery or chemotherapy
 To reduce or palliate symptoms
 Shrink tumors affecting quality of life,
e.g., a lung tumor causing shortness of
breath
 Alleviate pain or neurologic symptoms by
reducing the size of a tumor
External beam radiation
treatments are usually
scheduled five days a week
and continue for one to ten
weeks

12. RT in Multidisciplinary Care
 Radiation therapy plays a major role in
the management of many common
cancers either alone or as an adjuvant
therapy with surgery and chemotherapy
 Sites commonly treated include breast,
prostate, lung, colorectal, pancreas,
esophagus, head and neck, brain, skin,
gynecologic, lymphomas, bladder cancers
and sarcomas
 Radiation is also frequently used to treat
brain and bone metastases as well as
cord compression

13. RT
 PRIMARY
 ADJUVANT
 NEO-ADJUVANT
 CONCURRENT
 PALLIATIVE

14. Palliative RT
 Commonly used to relieve pain from bone cancers
 ~ 50 percent of patients receive total relief from
their pain
 80 to 90 percent of patients will derive some relief
 Other palliative uses:
 Spinal cord compression
 Vascular compression, e.g., superior vena cava
syndrome
 Bronchial obstruction
 Bleeding from gastrointestinal or gynecologic
tumors
 Esophageal obstruction
Radiation is effective therapy for relief
of bone pain from cancer

15. The Radiation Oncology Team
 Radiation Oncologist
 The doctor who prescribes and oversees the radiation therapy treatments
 Medical Physicist
 Ensures that treatment plans are properly tailored for each patient, and is
responsible for the calibration and accuracy of treatment equipment
 Dosimetrist
 Works with the radiation oncologist and medical physicist to calculate the
proper dose of radiation given to the tumor
 Radiation Therapist
 Administers the daily radiation under the doctor’s prescription and supervision
 Radiation Oncology Nurse
 Interacts with the patient and family at the time of consultation, throughout the
treatment process and during follow-up care

16. The Treatment Process
Referral
Consultation
Simulation
Treatment Planning
Quality Assurance

17. Referral
Tissue diagnosis has been
established
Referring physician reviews
potential treatment options
with patient
Treatment options may include
radiation therapy, surgery,
chemotherapy or a
combination
It is important for a referring physician to
discuss all possible treatment options available
to the patient

18. Consultation
Radiation oncologist
determines whether radiation
therapy is appropriate
A treatment plan is developed
Care is coordinated with other
members of patient’s oncology
team
The radiation oncologist will discuss with the
patient which type of radiation therapy
treatment is best for their type of cancer

19. Simulation
Patient is set up in treatment
position on a dedicated CT scanner
 Immobilization devices may be
created to assure patient comfort and
daily reproducibility
 Reference marks or “tattoos” may be
placed on patient
CT simulation images are often
fused with PET or MRI scans for
treatment planning
Aird EG, Conway J. CT simulation for radiotherapy treatment planning. The British
journal of radiology. 2002 Dec;75(900):937-49.

20. Treatment Planning
 Physician outlines the target
and organs at risk
 Sophisticated software is used to
carefully derive an appropriate
treatment plan
• Computerized algorithms enable the
treatment plan to spare as much
healthy tissue as possible
 Medical physicist checks the chart
and dose calculations
 Radiation oncologist reviews and
approves final plan
Radiation oncologists work with medical
physicists and dosimetrists to create the
optimal treatment plan for each individualized
patient

21. Treatment Planning
• Indication for radiotherapy
• Goal of radiation therapy
• Planned treatment volume
• Planned treatment technique
• Planned treatment dose
Radiation oncologists work with medical
physicists and dosimetrists to create the
optimal treatment plan for each individualized
patient

22. Safety and Quality Assurance
Each radiation therapy treatment plan goes through
many safety checks
 The medical physicist checks the calibration of the linear
accelerator on a regular basis to assure the correct dose is
being delivered
 The radiation oncologist, along with the dosimetrist and
medical physicist go through a rigorous multi-step QA
process to be sure the plan can be safely delivered
 QA checks are done by the radiation therapist daily to ensure
that each patient is receiving the treatment that was
prescribed for them

23. Delivery of RT
External beam radiation therapy
typically delivers radiation using a linear
accelerator
Internal radiation therapy, called
brachytherapy, involves placing
radioactive sources into or near the
tumor
The modern unit of radiation is the
Gray (Gy), traditionally called the rad
1Gy = 100 centigray (cGy)
1cGy = 1 rad
The type of treatment used will depend on
the location, size and type of cancer.

24. RT

25. Types of External Beam RT
Two-dimensional radiation therapy
Three-dimensional conformal radiation therapy
(3-D CRT)
Intensity modulated radiation therapy (IMRT)
Image Guided Radiation Therapy (IGRT)
Intraoperative Radiation Therapy (IORT)
Stereotactic Radiotherapy (SRS/SBRT)
Particle Beam Therapy

26. Clinical radiation generators
 Kilovoltage Units
 Van de Graaff Generator
 Linear Accelerator (linacs)
 Betatron
 Microtron
 Cyclotron
 Machine Using Radionuclides (Radium-226, Cesium-137,
Cobalt-60)
 Heavy Particle Beams

27. Three-Dimensional Conformal
Radiation Therapy (3-D CRT)
Uses CT, PET or MRI scans to
create a 3-D picture of the tumor
and surrounding anatomy
Improved precision,
decreased normal tissue
damage
Huq S, Mayles P, Besa C. Transition from 2-D radiotherapy to 3-D conformal and
intensity modulated radiotherapy. IAEA-TECDOC; 2008.

28. Intensity Modulated Radiation
Therapy (IMRT)
A highly sophisticated form of 3-D
CRT allowing radiation to be shaped
more exactly to fit the tumor
 Radiation is broken into many
“beamlets,” the intensity of each can
be adjusted individually
IMRT allows higher doses of radition
to be delivered to the tumor while
sparing more healthy surrounding
tissue
Huq S, Mayles P, Besa C. Transition from 2-D radiotherapy to 3-D conformal and
intensity modulated radiotherapy. IAEA-TECDOC; 2008.

29. Image Guidance
For patients treated with 3-D or
IMRT
Physicians use frequent imaging
of the tumor, bony anatomy or
implanted fiducial markers for daily
set-up accuracy
Imaging performed using CT scans,
high quality X-rays, MRI or ultrasound
Motion of tumors can be tracked to
maximize tumor coverage and
minimize dose to normal tissues
Fiducial markers in prostate
visualized and aligned

30. Stereotactic Radiosurgery (SRS)
SRS is a specialized type of external
beam radiation that uses focused
radiation beams targeting a well-
defined tumor
o SRS relies on detailed imaging, 3-D
treatment planning and complex
immobilization for precise treatment
set-up to deliver the dose with
extreme accuracy
o Used on the brain or spine
o Typically delivered in a single
treatment or fraction

31. Stereotactic Body Radiotherapy
(SBRT)
SBRT refers to stereotactic radiation
treatments in 1-5 fractions on
specialized linear accelerators
o Uses sophisticated imaging, treatment
planning and immobilization
techniques
 Respiratory gating may be necessary for
motions management, e.g., lung tumors
o SBRT is used for a number of sites:
spine, lung, liver, brain, adrenals,
pancreas
o Data maturing for sites such as
prostate

32. Proton Beam Therapy
 Protons are charged particles that
deposit most of their energy at a
given depth, minimizing risk to
tissues beyond that point
 Allows for highly specific targeting of
tumors located near critical
structures
 Increasingly available in the U.S.
 Most commonly used in treatment of
pediatric, CNS and intraocular
malignancies
 Data maturing for use in other tumor
sites
Proton Gantry
Source: Mevion

33. Types of Internal RT
Intracavitary implants
 Radioactive sources are placed in a cavity near
the tumor (vagina, cervix, uterine)
Interstitial implants
 Sources placed directly into the tissue (breast,
prostate)
Intra-operative implants
 Surface applicator is in direct contact with the
surgical tumor bed

34. Brachytherapy
• Radioactive sources are implanted
into the tumor or surrounding
tissue
125I, 103Pd, 192Ir, 137Cs
• Purpose is to deliver high doses of
radiation to the desired target
while minimizing the dose to
surrounding normal tissues
Radioactive seeds for a
permanent prostate implant,
an example of low-dose-rate
brachytherapy.

35. Brachytherapy Dose Rate
Low-Dose-Rate (LDR)
Radiation delivered over days and
months
Prostate, breast, head and neck, and
gynecologic cancers may be treated
with LDR brachytherapy
High-Dose-Rate (HDR)
High energy source delivers the dose in
a matter of minutes rather than days
Gynecologic, breast, head and neck,
lung, skin and some prostate implants
may use HDR brachytherapy
LDR prostate implant

36. Permanent vs. Temporary Implants
 Permanent implants release small amounts of radiation
over a period of several months
 Examples include low-dose-rate prostate implants (“seeds”)
 Patients receiving permanent implants may be minimally radioactive and
should avoid close contact with children or pregnant women
 Temporary implants are left in the body for several hours
to several days
 Patient may require hospitalization during the implant depending on the
treatment site
 Examples include low-dose-rate GYN implants and high-dose-rate prostate
or breast implants

37. Intraoperative Radiation Therapy
(IORT)
IORT delivers a concentrated
dose of radiation therapy to a
tumor bed during surgery
Advantages
Decrease volume of tissue in boost
field
Ability to exclude part or all of dose-
limiting normal structures
Increase the effective dose
Multiple sites
Pancreas, stomach, lung, esophagus,
colorectal, sarcomas, pediatric
tumors, bladder, kidney, gyn
Several recent trials have shown
efficacy for breast cancer

38. Systemic RT
Radiation can also be delivered by an injection.
 Metastron (89Strontium), Quadramet(153Samarium) and
Xofigo (223Radium) are radioactive isotopes absorbed
primarily by cancer cells
 Used for treating bone metastases
 Radioactive isotopes may be attached to an antibody
targeted at tumor cells
 Zevalin, Bexxar for Lymphomas
 Radioactive “beads” may be used to treat primary or
metastatic liver cancer
 Y90-Microspheres

39. RT Side effects and complications
 The delivery of external beam
radiation treatments is painless and
usually scheduled five days a week for
one to ten weeks
 The effects of radiation therapy are
cumulative with most significant side
effects occurring near the end of the
treatment course.
 Side effects usually resolve over the course
of a few weeks
 There is a slight risk that radiation may
cause a secondary cancer many years after
treatment, but the risk is outweighed by
the potential for curative treatment with
radiation therapy
{Sabin Motwani will
send us image of mild
skin redness after RT
in a treatment field}.
Example of erythroderma after
several weeks of radiotherapy with
moist desquamation
Source:
sarahscancerjourney.blogspot.com

40. Common Radiation SE
Side effects during the treatment vary depending on
site of the treatment and affect the tissues in radiation
field:
 Breast – swelling, skin redness
 Abdomen – nausea, vomiting, diarrhea
 Chest – cough, shortness of breath, esophogeal
irritation
 Head and neck – taste alterations, dry mouth,
mucositis, skin redness
 Brain – hair loss, scalp redness
 Pelvis – diarrhea, cramping, urinary frequency, vaginal
irritation
 Prostate – impotence, urinary symptoms, diarrhea
 Fatigue is often seen when large areas are irradiated
Modern radiation therapy techniques have decreased
these side effects significantly
Unlike the systemic side effects
from chemotherapy, radiation
therapy usually only impacts the
area that received radiation

41. AE, risk factors, treatment
Berkey FJ. Managing the adverse effects of radiation
therapy. Am Fam Physician. 2010 Aug 15;82(4):381-8.

42. AE, risk factors, treatment …

43. AE, risk factors, treatment …

44. Summary
Radiation therapy is a well established
modality for the treatment of numerous
malignancies
Radiation oncologists are specialists trained to
treat cancer with a variety of forms of
radiation
Treatment delivery is safe, quick and painless

45. Cancer immunotherapy
Facilitator:
Dr. Christina Malichewe
Presenter:
Basil Tumaini

46. Introduction
• Tumor immunotherapy requires the understanding of
tumor immunology to facilitate:
 understanding of the immunologic relationship between
the host and the tumor
 utilization of the immune response to tumors for
purpose of diagnosis, prophylaxis and therapy
Raval RR, Sharabi AB, Walker AJ, Drake CG, Sharma P. Tumor immunology and cancer immunotherapy:
summary of the 2013 SITC primer. Journal for immunotherapy of cancer. 2014 Dec;2(1):14.

47. How do cancer cells differ from normal?
 Clonal in origin
 Deregulated growth and lifespan
 Altered tissue affinity
 Resistance to control via apoptotic
signals
 Change in surface phenotype and markers
 Structural and biochemical changes
 Presence of tumour-specific antigens

48. 48
Tumor antigen
Classification of tumor antigen
– Old classification;-classified into two
categories based on their patterns of
expression:
– Tumor-specific antigens (TSA’s)
– Tumor-associated antigens (TAA’s)
Modern classification -based on their molecular
structure and source
Renkvist N, Castelli C, Robbins PF, Parmiani G. A listing of human tumor antigens recognized by T cells.
Cancer Immunology, Immunotherapy. 2001 Mar 1;50(1):3-15.

49. Old classification
 Tumor-specific antigens (TSA’s)
Antigens unique to cancerous cells and are not present on their
normal counterpar
 Bcr-abl (e.g. in CML)
 CDK-4 / β-catenin (melanoma)
 Tumor-associated antigens (TAA’s)
Antigens on tumor cells that
– are qualitatively not different from those found on normal
cells
– but are over expressed i.e present at significantly increased
numbers on the cancer cell as products of cellular
oncogenes

50. – e.g. high levels of a growth factor receptor due to
increased expression of neu oncogene products
found in a number of human breast cells
– And ras oncogene products is present on some
human prostatic cancer cells
Tumour associated antigens
•MUC-1 (myeloma etc)
•α-fetoprotein (many)
•Her-2/neu (breast)
•WT-1 (many)
•myeloblastin (leukaemias)
•Survivin (many)

51. • old classification, is imperfect, because many
antigens thought to be tumor specific turned
out to be expressed by some normal cells as
well.

52. Modern classification of tumor antigens
7 categories
• Differ in both factors that induce malignancy
and immunochemical properties of tumor
antigens
• Important development in tumor immunology
is identifying tumor antigens that were
recognized by cytotoxic T lymphocytes
(CTLs), because CTLs are the major immune
defense mechanism against tumors.

53. 1.Tumor Antigens Produced by Oncogenic Viruses
• there are viruses associated with cancers.
• these viruses produce proteins that are recognized as foreign
by the immune system.
• The most potent of these antigens are proteins produced by
latent DNA viruses; examples in humans include HPV and
EBV.
• There is abundant evidence that CTLs recognize antigens
of these viruses and that a competent immune system plays
a role in surveillance against virus-induced tumors because
of its ability to recognize and kill virus-infected cells.

54. - vaccines against HPV antigens have been found
effective in prevention of cervical cancers in
young females
-these antigens exhibit extensive immunologic cross
reactivity
– particular oncogenic virus induces expression of same
antigens in a tumor regardless of tissue origin or animal
species

55. 2. Oncofetal Antigens.
• Antigens present during embryonic and fetal
development
–but they are either absent or present at very
low levels in normal adult tissue
–Become expressed in tumors
–Not immunogenic in the host
–can be detected by antisera prepared
against them

56. • E.g. Carcinoembryonic antigen (CEA) found
primarily in serum of patients with cancer of
GIT esp cancer of colon
–But non specific
–Elevated levels also been in the patients with
some types of lung cancer, pancreatic cancer
breast and stomach cancer
–Also elevated in patients with emphysema,
ulcerative colitis and pancreatitis,alcoholics
and heavy smokers

57. • α fetoprotein (AFP), which is normally present
in high concentrations in fetal and maternal
serum but absent from normal individuals
–Secreted by cells of a variety of cancers and
is found particularly in patients with
hepatomas and testicular teratocarcinomas
• Occasionally, virally induced tumors may
express oncofetal antigens, encoded by the
host genome
• they are not entirely tumor specific, they can
serve as serum markers for cancer.

58. • Association of oncodevelopmental antigens
with a wide variety of tumor types strongly
suggests that derepression of normal genes that
are usually repressed in the normal adult
individual in a concomitant malignancy

59. 3.Products of other mutated genes
• Because of the genetic instability of tumor cells,
many different genes may be mutated in these
cells, including genes whose products are not
related to the transformed phenotype and have
no known function
• Products of these mutated genes are potential
tumor antigens

60. 3.Products of other mutated genes …
• These antigens are extremely diverse because
the carcinogens that induce the tumors may
randomly mutagenize virtually any host gene
and the class I MHC antigen-presenting pathway
can display peptides from any mutated cytosolic
protein in each tumor.
• Mutated cellular proteins are found more
frequently in chemical carcinogen- or radiation-
induced tumors because chemical carcinogens
and radiation mutagenize many cellular genes.

61. 4.Products of Mutated Oncogenes and Tumor Suppressor Genes.
• The products of altered(mutated) protooncogenes and tumor
suppressor genes are synthesized in the cytoplasm of the tumor
cells, and like any cytosolic protein, they may enter the class I
MHC antigen processing pathway and be recognized by CD8+ T
cells
• In addition, these proteins may enter the class II MHC antigen-
processing pathway in antigen-presenting cells that have
phagocytized dead tumor cells, and thus be recognized by CD4+
T cells also

62. 4. Products of Mutated Oncogenes and Tumor Suppressor
Genes …
• Because these altered proteins are not present in normal
cells, they do not induce self-tolerance. Some cancer
patients have circulating CD4+ and CD8+ T cells that
can respond to the products of mutated oncogenes such
as RAS, p53, and BCR-ABL proteins.
• Because the mutant proteins are present only in tumors,
their peptides are expressed only in tumor cells.
• Since many tumors may carry the same mutation, such
antigens are shared by different tumors.
• Hence exhibit extensive immunologic cross reactivity

63. 5.Over expressed or Aberrantly Expressed Cellular Proteins
• Tumor antigens may be normal cellular proteins that are
abnormally expressed in tumor cells and elicit immune
responses.
• some tumor antigens are structurally normal proteins that are
produced at low levels in normal cells and overexpressed in
tumor cells.
• This proteins in normal cell are produced in such small
amounts and in so few cells that it is not recognized by the
immune system and fails to induce tolerance.
• E.g One such antigen is tyrosinase, an enzyme involved in
melanin biosynthesis that is expressed only in normal
melanocytes and melanomas.

64. 5.Over expressed or Aberrantly Expressed Cellular Proteins …
• T cells from melanoma patients recognize peptides
derived from tyrosinase, raising the possibility that
tyrosinase vaccines may stimulate such responses to
melanomas; clinical trials with these vaccines are
ongoing. On face value it is surprising that these
patients are able to respond to a normal self-antigen.

65. 6. Altered Cell-Surface Glycolipids and Glycoproteins
• tumors express higher than normal levels
and/or abnormal forms of surface glycoproteins
and glycolipids, which may be diagnostic
markers and targets for therapy
• These altered molecules include gangliosides,
blood group antigens, and mucins

66. 6. Altered Cell-Surface Glycolipids and Glycoproteins …
• Many antibodies have been raised in animals
that recognize the carbohydrate groups or
peptide cores of these molecules. Although
most of the epitopes recognized by these
antibodies are not specifically expressed on
tumors, they are present at higher levels on
cancer cells than on normal cells.

67. • This class of antigens is a target for cancer therapy
with specific antibodies.
• Eg. Among the glycolipids expressed at high
levels in melanomas are the gangliosides GM2,
GD2, and GD3.
• E.g. of mucin expressed in carcinoma are CA-125
and CA-19-9, expressed on ovarian carcinomas,
and MUC-1, expressed on breast carcinomas.

68. 7. Cell Type-Specific Differentiation Antigens
• Tumors express molecules that are normally present on
the cells of origin. These antigens are called
differentiation antigens because they are specific for
particular lineages or differentiation stages of various
cell types.
• Their importance is as potential targets for
immunotherapy and for identifying the tissue of origin of
tumors

69. 7. Cell Type-Specific Differentiation Antigens …
• These differentiation antigens are typically normal self-
antigens, and therefore they do not induce immune
responses in tumor-bearing hosts.
• For example, lymphomas may be diagnosed as B cell-
derived tumors by the detection of surface markers
characteristic of this lineage, such as CD10 and CD20.
• Antibodies against these molecules are also used for
tumor immunotherapy.

70. Antitumor Effector Mechanisms
• Cell-mediated immunity is the dominant anti-
tumor mechanism in vivo
• Although antibodies can be made against
tumors, there is no evidence that they play a
protective role under physiologic conditions

71. Cellular mechanisms
• Destruction by cytotoxic cells
• Antibody dependent cell mediated cytotoxicity
(ADCC)
• Destruction by activated macrophages
• Destruction by natural killer (NK) cells
T Lymphocytes
The T cell is the primary cell responsible for direct
recognition and killing of tumor cells. T cells carry out
immunologic surveillance, then proliferate and destroy
newly transformed tumor cells after recognizing TAAs.

72. Cytotoxic T cells
• Cytotoxic T cells (CTLs) CD8+ T cells:
attaching to class I MHC -peptide complex,
they destroy cancer cells by perforating the
membrane with enzymes or by triggering an
apoptotic pathway.

73. 73
MAC or
B cell
(APC)
MHC 1
T
cytotoxic
cell
Perforins, apoptotic signals
Exogenous
antigen
T
cytotoxi
c
memory
cells
T
cytotoxic
effector
cells
T Cytotoxic
Cell Activity
in Tumor
Surveillance
Cancer
Cell
T
cytotoxic
cell
Endogenous
antigen
DIRECT PATHWAY
INDIRECT PATHWAY

74. Helper T cells
• CD4+ T cells: reacting to class II MHC peptide
complex, they secret cytokines.
• cytotoxic T cell response (Th1 helper T cells)
• antibody response (Th2 helper T cells)

75. Natural killer cells (NK)
• NK cells are lymphocytes that are capable of destroying
tumor cells without prior sensitization;
• they may provide the first line of defense against tumor
cells. After activation with IL-2, NK cells can lyse a wide
range of human tumors, including many that seem to be
nonimmunogenic for T cells.
• T cells and NK cells seem to provide complementary
antitumor mechanisms.
.

76. • Tumors that fail to express MHC class I antigens cannot be
recognized by T cells, but these tumors may trigger NK cells
because the latter are inhibited by recognition of normal
autologous class I MHC molecules
• The triggering receptors on NK cells are extremely diverse and
belong to several gene families.
• NKG2D proteins expressed on NK cells and some T cells are
important activating receptors.
• They recognize stress-induced antigens that are expressed on
tumor cells and cells that have incurred DNA damage and are at
risk for neoplastic transformation.

77. NATURAL KILLER CELL
NK
Target cell (infected or
cancerous)
Perforin and enzymes
killer activating receptor
Do not recognize tumor cell via antigen specific cell
surface receptor, but rather through receptors that
recognize loss of expression of MHC I molecules,
therefore detect “missing self” common in cancer.

78. 78
Tumor surveillance by NK Cells
Tumor cells produce reactive oxygen species and stress induced ligands that
can be recognized by NK cells

79. Macrophages
• Macrophages can kill specific tumor cells when activated
by a combination of factors, including lymphokines
(soluble factors produced by T cells) and interferon.
• Activated macrophages exhibit cytotoxicity against tumor
cells in vitro.
• T cells, NK cells, and macrophages may collaborate in
antitumor reactivity, because interferon-γ, a cytokine
secreted by T cells and NK cells, is a potent activator of
macrophages.

80. • Activated macrophages may kill tumors by
mechanisms similar to those used to kill microbes
(e.g., production of reactive oxygen metabolites;) or
by secretion of tumor necrosis factor (TNF).
• tumor necrosis factor (TNF-) that has potent
antitumor activity.
• When TNF- is injected into tumor bearing animals,
it has been found to induce hemorrhage and necrosis
of the tumor

81. Dendritic cells
• Dendritic cells are dedicated antigen-
presenting cells present in barrier tissues (eg,
skin, lymph nodes). They play a central role in
initiation of tumor-specific immune response.
Palucka K, Banchereau J. Cancer immunotherapy via dendritic cells. Nature Reviews Cancer.
2012 Apr;12(4):265.

82. Humoral Mechanisms
• Although there is no evidence for the protective
effects of anti-tumor antibodies against
spontaneous tumors, administration of
monoclonal antibodies against tumor cells can be
therapeutically effective.
• A monoclonal antibody against CD20, a B cell
surface antigen, is widely used for treatment of
certain non-Hodgkin lymphomas.

83. Antibody - produced by B cells
Direct attack: blocking growth factor receptors, arresting
proliferation of tumor cells, or inducing apoptosis
-- is not usually sufficient to completely protect the body
Indirect attack: -- major protective efforts
(1)ADCC(antibody-dependent cell mediated cytotoxicity )
-- recruiting cells that have cytotoxicity, such as monocytes and
macrophages
(2) CDC (complement dependent cytotoxicity)
-- binding to receptor, initiating the complement system,
'complement cascade’, resulting in a membrane attack complex,
causing cell lysis and death

84. 84
MAC
MHC II
MHC I
APC
T
helper
cell
T
helper
2 cell
IL-2
B Cell Eosinophil
IL-4 IL-5
T
helper
Memor
y cell
T
helper
Effector
cell
IL-1
T
cytotoxic
cell
T
cytotoxi
c
memory
cells
T
cytotoxic
effector
cells
Perforins, apoptotic signals
Interferon
1
Cancer
Cell
T
cytotoxic
cell
Endogenous
antigen
Perforins, apoptotic signals
Generally
ineffective
tumor
surveillance,
but some
ADCC
Tumor
antigen or
tumor cell
SUMMARY

85. Immunosurveillance
• Theory formulated in 1957 by Burnet and
Thomas, who proposed that lymphocytes act
as sentinels in recognizing and eliminating
continuously arising, nascent transformed
cells.
• An important host protection process that
inhibits carcinogenesis and maintains regular
cellular homeostasis

86. Immunoediting
• Immunoediting is a process by which a person is protected from
cancer growth and the development of tumour immunogenicity by
their immune system.
• It has three main phases:
– elimination
– equilibrium and
– escape
• The elimination phase consists of the following four phases
Dunn GP, Bruce AT, Ikeda H, Old LJ, Schreiber RD. Cancer immunoediting: from
immunosurveillance to tumor escape. Nature immunology. 2002 Nov;3(11):991.
Mittal D, Gubin MM, Schreiber RD, Smyth MJ. New insights into cancer immunoediting and its three
component phases—elimination, equilibrium and escape. Current opinion in immunology. 2014 Apr 1;27:16-
25.

87. Elimination: Phase 1
• The first phase of elimination involves the initiation of
antitumor immune response.
• Cells of the innate immune system recognise the presence
of a growing tumor which has undergone stromal
remodeling, causing local tissue damage
This is followed by the induction of inflammatory signals
which is essential for recruiting cells of the innate immune
system. (eg. natural killer cells, natural killer T cells,
macrophages and dendritic cells) to the tumor site.
production of IFN-gamma

88. Elimination: Phase 2
• In the second phase of elimination, newly
synthesised IFN-gamma induces tumor death (to a
limited amount) as well as promoting the
production of chemokines CXCL10, CXCL9 and
CXCL11.
• These chemokines play an important role in promoting
tumor death by blocking the formation of new blood
vessels.
• Tumor cell debris produced as a result of tumor death is
then ingested by dendritic cells, followed by the migration
of these dendritic cells to the draining lymph nodes.
• The recruitment of more immune cells also occurs and is
mediated by the chemokines .

89. Elimination: Phase 3
• In the third phase, natural killer cells and
macrophages transactivate one another via the
reciprocal production of IFN-gamma and IL-12.
• This again promotes more tumor killing by these cells
via apoptosis and the production of reactive oxygen
and nitrogen intermediates
• In the draining lymph nodes, tumor-specific dendritic
cells trigger the differentiation of Th1 cells which in
turn facilitates the development of CD8+ T cells

90. Elimination: Phase 4
• In the final phase of elimination, tumor-
specific CD4+ and CD8+ T cells home to
the tumor site and the cytolytic T
lymphocytes then destroy the antigen-
bearing tumor cells which remain at the
site.

91. Equilibrium and Escape
• Tumor cell variants which have survived the elimination
phase enter the equilibrium phase.
• lymphocytes and IFN-gamma exert a selection pressure on
tumor cells which are genetically unstable and rapidly
mutating.
• Tumor cells continue to grow and expand in an uncontrolled
manner and may eventually lead to malignancies.
• In the study of cancer immunoeditting, knockout mice have
been used for experimentation since human testing is not
possible.

92. 92
Basic Tumor Immunosurveillance
Smyth, M. J. et al. Nature Immunology 2, 293 - 299 (2001)
1) The presence of tumor
cells and tumor antigens
initiates the release of
“danger” cytokines such
as IFN and heat shock
proteins (HSP).
2) These cause the
activation and maturation
of dendritic cells such
that they present tumor
antigens to CD8 and CD4
cells
3) subsequent T cytotoxic
destruction of the tumor
cells the occurs

93. 93
Tumor Escape Mechanisms
• Low immunogenicity
• Antigen modulation
• Lack of costimulation
• Immune suppression by tumor cells or T
regulatory cells
• Antige n masking
• Apoptosis of cytotoxic T cells

94. Low immunogenicity
• Selective outgrowth of antigen-negative
variants: During tumor progression, strongly
immunogenic subclones may be eliminated

95. Antigen modulation
• Loss or reduced expression of MHC molecules:
Tumor cells may fail to express normal levels
of HLA class I molecules, thereby escaping
attack by cytotoxic T cells. Such cells, however,
may trigger NK cells.

96. Lack of costimulation
• Lack of costimulation: It may be recalled that
sensitization of T cells requires two signals, one by
foreign peptide presented by MHC molecules and the
other by costimulatory molecules although tumor cells
may express peptide antigens with class I molecules,
they often do not express costimulatory molecules. This
not only prevents sensitization, but also may render T
cells anergic or, worse, cause them to undergo
apoptosis.
•

97. Immunosuppression
• Many oncogenic agents (e.g., chemicals and
ionizing radiation) suppress host immune
responses. Tumors or tumor products may also be
immunosuppressive. For example, TGF-β,
secreted by many tumors, is a potent
immunosuppressant. In some cases, the immune
response induced by the tumor (e.g., activation of
regulatory T cells) may itself inhibit tumor
immunity.

98. 98
1) Tumor cell production of immune suppressants such as
TGF-,
2) T regulatory cell stimulation with production of
immune suppressants such as TGF- 
1 2
Avoidance of tumor surveillance through
release of immune suppressants
Mapara Journal of Clinical Oncology. 22(6):1136-51, 2004

99. Antigen masking:
• Antigen masking: The cell-surface antigens of
tumors may be hidden, or masked, from the
immune system by glycocalyx molecules, such
as sialic acid-containing mucopolysaccharides.
This may be a consequence of the fact that
tumor cells often express more of these
glycocalyx molecules than normal cells do.

100. Apoptosis of cytotoxic T cells
• Apoptosis of cytotoxic T cells: Some
melanomas and hepatocellular carcinomas
express Fas ligand. It has been postulated that
these tumors kill Fas-expressing T
lymphocytes that come in contact with them,
thus eliminating tumor-specific T cells

101. 101
Tumor cells induce apoptosis in T lymphocytes
via FAS activation
1) Cancer cells express FAS
ligand
2) Bind to FAS receptor on T
lymphocytes leading to
apoptosis

102. 102
TUMOR ESCAPE MECHANISMS
T regulatory cells
Or kill them
Or T regulatory cells

103. Clinical Tumor Immunology
• Immunodiagnosis
• Immunoprophylaxis
• Immunotherapy

104. Immunodiagnosis
May be performed to achieve two separate goals
– Immunological detection of antigens specific to
tumor cells
– Assessment of hosts immune response to tumor

105. Immunodiagnosis …
Detection of tumor cells and their products by
immunological means
– Myeloma and Bence-Jones proteins e.g. plasma cell tumor
– AFP e.g. Liver cancer
– CEA e.g. GIT cancers
– PSA
– Immunological detection of other tumor cell markers e.g.
enzymes and hormones
– Detection of tumor specific antigens in the circulation or by
immunoimaging

106. Detection of anti tumor immune response
• Anti tumor antibodies
• Anti tumor cell mediated immunity

107. Cancer Immunotherapy
• Manipulation of Co-Stimulatory Signal
• Enhancement of APC Activity
• Cytokine Therapy
• Monoclonal Antibodies
• Cancer Vaccines

108. 1863 1898 1957 1983 1985 1991, 4 2002 2009 2010 2011 2014
Description of
immune
infiltrates in
tumors by
Virchow
Treatment of
cancer with
bacterial
products
(“Coley’s toxin”)
Cancer
immuno-
surveillance
hypothesis
(Burnet,
Thomas)
1976
Treatment
of bladder
cancer with
BCG
IL-2
therapy for
cancer
Adoptive
cell therapy
Discovery of
human
tumor
antigens
(Boon,
others)
Adoptive T
cell therapy
HPV
vaccination
in VIN
FDA approval of
sipuleucel-T (DC
vaccine) in
prostate cancer
FDA approval of
anti-CTLA4
(ipilumimab) for
melanoma
FDA approval of
anti-PD1 for
melanoma
The history of cancer immunotherapy: from empirical
approaches to rational, science-based therapies
Mellman I, Coukos G, Dranoff G. Cancer immunotherapy comes of age. Nature; 2011 Dec
21;480:480. Available from: http://dx.doi.org/10.1038/nature10673

109. Manipulation of Co-Stimulatory Signal
• Tumor immunity can be enhanced by providing the co-
stimulatory signal necessary for activation of CTL
precursors (CTL-Ps)
• Fig. 22.11a

110. Manipulation of Co-Stimulatory Signal
Cont.
• Basis for Vaccine
– Prevent metastasis after surgical removal or
primary melanoma in human patients

111. Enhancement of APC Activity
• GM-CSF (Granulocyte-macrophage colony-
stimulating factor)
remember: CSFs are cytokines that induce the formation
of distinct hematopoietic cell lines
• Fig 22.11b

112. Cytokine Therapy
• Use of recombinant cytokines (singly or in
combination) to augment an immune
response against cancer
– Via isolation and cloning of various cytokine genes
such as:
– IFN-α, β, and γ
– Interleukin 1, 2, 4, 5, and 12
– GM-CSF and Tumor necrosis factor (TNF)

113. Cytokine Therapy Cont.
I. Interferons
• Most clinical trials involve IFN-α
• Has been shown to induce tumor regression in
hematologic malignancies i.e. leukemias,
lymphomas, melanomas and breast cancer
• All types of IFN increase MHC I expression
• IFN-γ also has also been shown to increase MHC
II expressionon macrophages and increase
activity of Tc cells, macrophages, and NKs

114. Cytokine Therapy Cont.
II. Tumor Necrosis Factors
• Kills some tumor cells
• Reduces proliferation of tumor cells without
affecting normal cells
How?
• Hemorrhagic necrosis and regression, inhibits
tumor induced vascularization (angio-genesis)
by damaging vascular endothelium

115. Cytokine Therapy Cont.
III. In Vitro-Activited LAK & TIL cells
A. Lymphocytes are activated against tumor
antigens in vitro
• Cultured with x-irradiated tumor cells in
presence of IL-2
• Generated lymphokine activated killer
cells (LAKs), which kill tumor cells
without affecting normal cells

116. In Vitro-Activated LAK and TIF cells Cont.
B. Tumors contain lymphocytes that have
infiltrated tumor and act in anti-tumor
response
• via biopsy, obtained cells and
expanded population in vitro with
• generated tumor-infiltrating lympho-
cytes (TILs)

117. Tumor immunoprophylaxis
• Immunization against tumor itself requires
that the tumor possess specific antigens and
that these antigens cross react
immunologically with any prepared vaccine
• Efficacy of immunoprophylaxis for protection
of humans and animals against spontaneous
tumors has not been sufficiently evaluated

118. 118
Tumor Vaccines
• Killed tumor cells
• Purified tumor antigens
• DNA vaccines
• Dendritic cell vaccines

119. Pretherapy Week 4 Week 6
Injected
lesion
Clinical response of anti-PD1 refractory melanoma patient
treated with anti-PD1 plus in situ CMP-001
Photos courtesy of M. Milhem

122. Other references
• Levinson WE. Review of Medical Microbiology and
Immunology 15E. McGraw Hill Professional; 2018 Jun 22
• Kumar V, Cortran RS, Robbins SL. Robins basic Pathology. 7th
Edison. Saunders. Philadelphia. 2003:960-9
• Raval RR, Sharabi AB, Walker AJ, Drake CG, Sharma P. Tumor
immunology and cancer immunotherapy: summary of the
2013 SITC primer. Journal for immunotherapy of cancer. 2014
Dec;2(1):14