1. Understanding
Cancer
&
Radiation Therapy
Dr. T. Sujit
Consultant Radiation Oncologist
Comprehensive Cancer Care Network
BASI CS OF ONCOLOGY
www.cccn.org.in

2. What is Cancer?
• A group of diseases
• Characterised by uncontrolled growth of abnormal
cells.
• Local destruction/Infiltration.
• Spread to other parts of the body – (metastasis)

3. Oncology
• Greek - ONKOS - tumor , LOGY – study
• Surgical Oncology
• Medical Oncology
• Radiation Oncology
• Nursing Oncology
• Psycho-Social Oncology

4. - ORIGIN OF CANCER -
Are all forms of cancer the same?
No. . . .
Cancer originates in different tissues and has different
etiologies.
First, normal cells are damaged somehow. This is called
initiation.
Second, the cells which have been initiated, experience
further “insults” known as promotion and are transformed
into “PRE-CANCEROUS CELLS” over a period of years.
The pre-cancerous cells then progress to frank cancer in a
short period.

5. STEPS IN THE INDUCTION OF
CANCER
PRE-CARCINOGEN
METABOLIC
ACTIVATION
DNA ADDUCTS
NORMAL CELL
DNA REPAIR
INITIATED
CELL
PRE-
NEOPLASTIC
CELL
NEOPLASTIC
CELL
1-2
DAYS 10 + YRS 1 + YR
R
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P
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N
P
R
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M
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T
I
O
N
P
R
O
G
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S
S
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O
N

7. TYPES OF CANCER
Carcinoma: Cancer of the skin and the tissues that line
the body. Includes lung cancer, breast cancer, cervical
cancer, head & neck cancer, stomach & bowel cancer etc.
Sarcoma: Cancer of bone and muscle tissue
Lymphoma and Leukemia ( “blood cancer ”) : Cancer
originating from the lymph and bone marrow tissues.

8. Risk factors for cancer
• Tobacco use
• Unbalanced diet- High fat intake
Low fibre diet
• Sedentary lifestyle
• Unsafe sex
• Ultraviolet Radiation
• Chronic Alcohol Use

9. Oral cavity, G I Tract
Limit consumption of
alcohol
Chronic Alcohol Use
Skin
Avoid excessive sun
exposure. Do not use
artificial tanning devices
Ultraviolet Radiation
Liver; Cervix
Practice safer sex to reduce
exposure to sexually
transmitted diseases
Unsafe sex
Breast,
colorectal
Get regular moderate
physical activity
Sedentary lifestyle
Colon-rectum
Breast, Uterus
Eat more fruits and
vegetables
Unbalanced diet
Lung, Head & Neck
Bladder,G I Tract
Do not use tobacco
Avoid second hand tobacco
smoke
Tobacco use
Associated Cancer
Type
Lifestyle ModificationRisk Behaviors

10. PREVENTION
TERMINAL CARE
SCREENING
DIAGNOSIS & STAGING
TREATMENT
CONTINUING CARE & REHABILITATION

12. What is Radiation ?
• A form of invisible ENERGY
• Propagated as ELECTROMAGNETIC WAVES
• Radiation exists naturally
– Sun, Uranium, Radium, Radon gas etc.
• Can also be produced artificially
– X-ray machines, proton / neutron beam accelerators,
nuclear reactors etc.

13. Ionizing Radiation

14. The basic idea behind radiation therapy is to destroy the
tumour through high doses of radiation:

Mechanism of Action

15. The main target is the DNA which, when damaged, can lead to
cell death and therefore tumour necrosis.
Mechanism of Action

16. What is RADIATION THERAPY ?
• Use of controlled radiation beams to kill cancer cells.
• External Radiation ( EBRT ):
– Radiation comes from a machine outside the body and is
directed towards the cancer.
• Internal Radiation :
– The radiation comes from a radioactive source placed in
seeds, needles, or thin plastic tubes that are put in or near the
tissue.
• Systemic Radiation :
– The radioactive source in the form of a liquid is injected or
swallowed by the patient . The radioactive source is distributed
throughout the body.

17. The Radiation Therapy team
• RADIATION ONCOLOGIST
– A doctor who specializes in using radiation to treat cancer
• RADIATION DOSIMETRIST
– Determines the proper radiation dose
• RADIATION PHYSICIST
– Makes sure that the machine delivers the right amount of
radiation to the correct site in the body
• RADIATION THERAPIST
– Carries out the radiation treatment

18. External Radiation Therapy
• Radiation delivered in a controlled manner
from machines outside the body.
• Outpatient treatment
• Different types of radiation:
– Photons, electrons, protons, neutrons

19. Treatment Process

20. External Radiation Therapy
• Cobalt machines use a natural radioactive source –
Radioactive 60Cobalt – to deliver photon radiation.
• Newer machines – LINEAR ACCELERATORs ( LINAC )
– produce radiation artificially ; can produce both
photon and electron beams.
• IORT – Intra Operative RadioTherapy- uses a LINAC
inside an operation theatre to deliver radiation to
the cancerous growth exposed by the surgeon.

21. External Radiation Therapy
• Treatment machines are placed inside a specially
constructed room with thick walls to prevent radiation
leak.
• Used to treat a variety of cancers like head & neck
cancers, breast cancer, cervical cancer, lung cancer, brain
cancer.
• Maybe combined with Internal radiation , surgery or
chemotherapy as part of the treatment.

22. Radiation Therapy Planning
• Process whereby the radiation therapy team determines the
amount, type of radiation the patient will receive and the
optimal method to deliver that radiation for that particular
patient.
• Simulation – process where the patient is made to lie on a
couch on an X-ray machine or CT scanner and tattoo marks are
placed on the patients body to
– denote the areas which should be irradiated and
– to define the direction and point of entry of the radiation beam.

23. Treatment Overview

24. Radiation Therapy – External
As the tumour is normally surrounded by normal tissue and
often far away from the body surface, collateral damage of the
surrounding normal tissue by external radiation cannot be
avoided.

Radiation Therapy
Normal Tissue Side Effects

25. Multi-beam treatments
• Used if a high dose is
required to kill tumours
deeper in the body
• Several beams used
• Beams only overlap in the
tumour area
• Tumour receives fatal dose
but healthy cells receive a
lower, safer dose. Each of these
beams delivers 1/3
of the required
dose.

26. Sensitive
areas such
as the
eyes and
spinal cord
must be
avoided.
brain
eyes
tumour

27. What is 3D CRT ?
• 3 DIMENSIONAL CONFORMAL RADIOTHERAPY
– Is a sophisticated technique of delivering external
beam radiation.
– It involves targetting the tumor using multiple beams
from different directions.
– It reduces the side effects of radiation by minimising
the amount of normal tissue falling within the
radiation beam path.

28. What is I M R T?
• INTENSITY MODULATED RADIATION THERAPY
– Another sophisticated technique of delivering
external beam radiation.
– Can deliver more dose to the tumor alone sparing
the normal tissue.
– Results in better tumor control and minimal side
effects.
– Requires a LINAC machine.

29. Internal Radiation Therapy
( Brachytherapy)
• Uses radioactive sources in the form of seeds or pellets
• Inserted directly into the tumor or placed inside an
applicator and directed close to the tumor.
• Delivers very high amounts of radiation to the tumor since
the radioactive source is within or very near the tumor.
• In-patient treatment.

30. Internal Radiation Therapy
( Brachytherapy)
• INTRACAVITARY BRACHYTHERAPY
– Applicators are placed inside a hollow organ.
Eg. Ca cervix, Cancer of the uterus.
• INTRALUMINAL BRACHYTHERAPY
– Applicators are placed inside a tubular organ.
Eg. Ca esophagous, Ca lung.
• INTERSTITIAL BRACHYTHERAPY
– Involves inserting steel or plastic needle-like applicators
through the tumor. Eg. Ca tongue, Ca buccal mucosa,
breast cancer, prostate cancer (seed implants)

34. Radiation therapy
– when, how, why?
• Radiation therapy maybe used alone or in combination
with surgery and/or chemotherapy to treat a cancer
• NEO-ADJUVANT RT:
– When RT precedes surgery, it is called pre-op RT or
neo-adjuvant RT.
– It is used to downstage or reduce the tumor size and
make it easier for the surgeon to operate.

35. Radiation therapy
– when, how, why?
• ADJUVANT RT :
– When RT follows surgery, it is called post-op RT or adjuvant RT.
– Kills microscopic cancer cells which may have been left behind
after the surgery, thereby preventing recurrence of the cancer.
• CONCURRENT CHEMORADIATION:
– RT and chemotherapy are given together.
– Double benefit – RT has a local action and chemotherapy has
a local and systemic action.
– Can be a sole mode of treatment ( H & N cancers, cervical
cancer ) or in conjunction with surgery ( esophagous, rectum)

36. Radiation therapy
– when, how, why?
• PROPHYLACTIC RT:
– RT is given to a particular site in the absence of any gross
disease , to prevent occurrence of disease at that site.
Eg. Prophylactic cranial irradiation for leukemia patients.
• PALLIATIVE RT :
– RT is given with an intent to alleviate the symptoms of the
patient like bone pain, spinal cord compression, severe
breathlessness due to obstruction of vessels in the chest
( SVC syndrome ), bleeding from the tumor etc.

37. Side effects of Radiation Therapy
• Depends on area treated.
• Can be acute or chronic.
• Acute reactions are temporary and well manageable.
• Chronic reactions occur late and are distressing to the patient.
• Use of sophisticated techniques and drugs can reduce the
incidence of adverse effects.
• RISK OF SECONDARY RADIATION INDUCED CANCERS

38. PATIENTS RECEIVING
EXTERNAL BEAM
RADIATION THERAPY
ARE NOT
RADIOACTIVE