Introduction to Radiation Therapy

ByDr. Amr A. Abd-Elghany

Introduction to Radiation Oncology

• Radiation has been an effective tool for treating cancer for more than 100 years.

• Radiation oncologists are doctors trained to use radiation to eradicate cancer.

• About two-thirds of all cancer patients will receive radiation therapy as part of their treatment.

Brief History of Radiation Therapy

• The first patient was treated with radiation in 1896, two months after the discovery of the X-ray.

• Back then, both doctors and non-physicians treated cancer patients with radiation.

• Rapid technology advances began in the early 1950s with cobalt units followed by linear accelerators a few years later.

• Recent technology advances have made radiation more effective and precise.

What Is Radiation Therapy?

• Radiation therapy works by damaging the DNA within cancer cells and destroying their ability to reproduce.

• When the damaged cancer cells are destroyed by radiation, the body naturally eliminates them.

• Normal cells can be affected by radiation, but they are able to repair themselves.

• Sometimes radiation therapy is the only treatment a patient needs.

• Other times, it is combined with other treatments, like surgery and chemotherapy.

Objectives of RadiotherapyRadiation therapy is used :• To cure cancer (Radical

RT):– Destroy tumors that have

not spread to other body parts.

– Reduce the risk that cancer will return after surgery or chemotherapy.

• To reduce symptoms (Palliative RT):– Shrink tumors affecting

quality of life, like a lung tumor that is causing shortness of breath.

– Alleviate pain by reducing the size of a tumor.

Meet the Radiation Oncology Team

• Radiation Oncologist– The doctor who oversees the

radiation therapy treatments.• Medical Radiation Physicist

– Ensures that complex treatment plans are properly tailored for each patient.

• 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– Cares for the patient and family by

providing education, emotional support and tips for managing side effects.

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Types of Radiation Therapy

• Radiation therapy can be delivered two ways – externally and internally. – External beam radiation

therapy delivers radiation using a linear accelerator.

– Internal radiation therapy, called brachytherapy or seed implants, involves placing radioactive sources inside the patient.

• The type of treatment used will depend on the location, size and type of cancer.

External Beam

Radiotherapy (EBRT)

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External Beam radiotherapy (EBRT)

Basic principles• Treatment with beams of ionizing radiation

produced from a source external to the patient. Superficial tumors are often treated with X-rays of low energy, in the range 80-300 kV. The beam size is selected by using metal cone-shaped applicators of different sizes.

Limitations• Delivery of high dose to the skin• Rapid “ fall off ” of dose with depth• Higher absorbed dose in bone

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Megavoltage Radiation Therapy• Use of megavoltage X-rays produced by linear

accelerators. • Energies in the range 4-20 MV. • Higher penetration, higher dose rate, and better

collimation than beams of Co-60.

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Advantages• Maximum dose below skin surface• Skin sparing• Absorbed dose increased with depth• Sharp 'fall off' of dose at beam edge• Beam shape modified by collimators• Treatment from any direction can be used• Crossfire technique with 2-4 beams gives higher

target dose

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External Radiation Therapy– Proton Beam Therapy

• Uses protons rather than X-rays to treat certain types of cancer.

• Allows doctors to better focus the dose on the tumor with the potential to reduce the dose to nearby healthy tissue.

– Neutron Beam Therapy• A specialized form of radiation

therapy that can be used to treat certain tumors that are very difficult to kill using conventional radiation therapy.

– Stereotactic Radiotherapy• Sometimes called stereotactic

radio surgery, this technique allows the radiation oncologist to precisely focus beams of radiation to destroy certain tumors, sometimes in only one treatment.

Radiotherapy fractionationObjective• To achieve the required level of effect on the

tumor with the minimal effect to surrounding normal tissues.

Number of treatmentsAdvantages of few fractions:• Fewer attendances• Sparing of resources• Quicker response.Advantages of many fractions:• Less severe acute and late reactions• Higher tumor doses can be achieved, so giving

the greatest chance of cure.

Stereotactic RadiosurgeryAlternative Names• Gamma knife; • Cyberknife; • Stereotactic radiotherapy.

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Stereotactic radiosurgery• Stereotactic radiosurgery is a form of

radiation therapy that focuses high-powered x-rays on a small area of the body.

• Other types of radiation therapy can affect nearby healthy tissue, Stereotactic radiosurgery better targets the abnormal area.

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Why the Procedure is Performed

• Stereotactic radio surgery is often used to slow down the growth of small, deep brain tumors that are hard to remove during surgery.

• Such therapy may also be used in patients who are unable to have surgery, such as the elderly or those who are very sick.

• Radio surgery may also be used after surgery to treat any remaining abnormal tissue.

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Total Body Irradiation

(TBI)

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TBI involves irradiation of the entire body

•To improve cure rates for sensitive tumors •To eradicate residual cancer cells . •To prevent relapse (leukemia, lymphoma)•Preparative regimen for organ (bone marrow) transplantation to destroy or suppress the recipient's immune system, preventing immunologic rejection of transplanted organ (bone marrow)

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Patient pre-treatment screening• There should be adequate renal,

cardiac, hepatic, and pulmonary function to cope with the toxicity of chemotherapy and TBI.

Disadvantages• The maximum risk of damage is to

the lung.

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Brachytherapy

(Internal Radiation

Therapy)

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Brachytherapy (internal radiation therapy)

• A form of radiation treatment where the radiation sources are placed within or close to the target volume i.e. the sources are placed at the heart of the tumor. It allows minimal dose to normal tissue.

• Radioactive sources used are thin wires, rods, capsules or seeds.

• These can be either permanently or temporarily placed in the body.

Indications• The extent of the neoplasm must be

known precisely.• The site should be accessible for both

inserting and removing sources.

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Permanent Brachytherapy is often performed for prostate cancer using "seeds" - small radioactive rods

implanted directly into the tumor. 29

Advantages

• Allows the delivery of a localized high radiation dose.

• Low radiation risk

Disadvantages

• Staff (nursing and medical staff ) exposure to radiation

• Large tumors are usually unsuitable• Accurate positioning of sources requires

special skills.• Lymph nodes will not be irradiated by the

implant or intracavity treatment. 30

Body sites in which Brachytherapy can be used to treat cancer

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Types

Intracavity• radioactive material into body cavities• Uses : gynae cancers, bronchial cancers,

oesophageal cancers, bile duct cancer

Interstitial • radioactive material in tissues• Uses : breast cancer, tongue cancer, floor

of mouth cancer, anal cancer

Surface of tumour• Uses : skin, eye 32

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Side Effects of Radiation Therapy

• Side effects, like skin tenderness, are generally limited to the area receiving radiation.

• Unlike chemotherapy, radiation usually doesn’t cause hair loss or nausea.

• Most side effects begin during the second or third week of treatment.

• Side effects may last for several weeks after the final treatment.

Is Radiation Therapy Safe?

• Many advances have been made in the field to ensure it remains safe and effective.

• Multiple healthcare professionals develop and review the treatment plan to ensure that the target area is receiving the dose of radiation needed.

• The treatment plan and equipment are constantly checked to ensure proper treatment is being given.