Understanding Cancer

&Radiation Therapy

Dr. T. SujitConsultant Radiation OncologistComprehensive Cancer Care Network

BASICS OF ONCOLOGY

www.cccn.org.in

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)

Oncology

• Greek - ONKOS - tumor , LOGY – study

• Surgical Oncology • Medical Oncology• Radiation Oncology• Nursing Oncology• Psycho-Social Oncology

- 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.

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 +

YRS1 + YR

REPLICATION

PROMOTION

PROGRESSION

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.

Risk factors for cancer

• Tobacco use

• Unbalanced diet- High fat intake Low fibre diet

• Sedentary lifestyle

• Unsafe sex

• Ultraviolet Radiation

• Chronic Alcohol Use

Oral cavity, G I TractLimit consumption of

alcoholChronic Alcohol Use

SkinAvoid 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-rectumBreast, Uterus

Eat more fruits and vegetables

Unbalanced diet

Lung, Head & NeckBladder,G I Tract

Do not use tobaccoAvoid second hand

tobacco smoke Tobacco use

Associated CancerType

Lifestyle ModificationRisk Behaviors

PREVENTION

TERMINAL CARE

SCREENING

DIAGNOSIS & STAGING

TREATMENT

CONTINUING CARE & REHABILITATION

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.

Ionizing Radiation

The basic idea behind radiation therapy is to destroy the tumour through high doses of radiation:

Mechanism of Action

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

Mechanism of Action

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.

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

External Radiation Therapy

• Radiation delivered in a controlled

manner from machines outside the

body.

• Outpatient treatment

• Different types of radiation:

– Photons, electrons, protons, neutrons

Treatment Process

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.

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.

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.

Treatment Overview

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

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.

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

brain

eyes

tumour

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.

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.

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.

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)

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.

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)

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.

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

PATIENTS RECEIVING EXTERNAL BEAM

RADIATION THERAPY ARE NOT

RADIOACTIVE