Radiation Oncology in India
Radiation oncology is a medical specialty that involves treating cancer with radiation. Doctors who specialize in treating cancer with radiation (radiation oncologists) use radiation therapy to treat a wide variety of cancers.
Radiation therapy uses carefully targeted and regulated doses of high-energy radiation to kill cancer cells. Radiation causes some cancer cells to die immediately after treatment, but most die because the radiation damages the chromosomes and DNA so that the cells can no longer divide and the tumor can’t grow.
The type of radiation therapy prescribed by a radiation oncologist depends on many factors, including:
- The type of cancer.
- The size of the cancer.
- The cancer’s location in the body.
- How close the cancer is to normal tissues that are sensitive to radiation.
- How far into the body the radiation needs to travel.
- The patient’s general health and medical history.
- Whether the patient will have other types of cancer treatment.
- Other factors, such as the patient’s age and other medical conditions.
Radiation Therapy Treatment Options
Radiation can come from a machine outside the body (external-beam radiation therapy) or from radioactive material placed in the body near cancer cells (internal radiation therapy, more commonly called brachytherapy)
External-beam radiation therapy
Intensity-modulated radiation therapy (IMRT): IMRT uses hundreds of tiny radiation beam-shaping devices, called collimators, to deliver a single dose of radiation (2). The collimators can be stationary or can move during treatment, allowing the intensity of the radiation beams to change during treatment sessions. This kind of dose modulation allows different areas of a tumor or nearby tissues to receive different doses of radiation.
Image-guided radiation therapy (IGRT): In IGRT, repeated imaging scans (CT, MRI, or PET) are performed during treatment. These imaging scans are processed by computers to identify changes in a tumor’s size and location due to treatment and to allow the position of the patient or the planned radiation dose to be adjusted during treatment as needed.
Tomotherapy: Tomotherapy is a type of image-guided IMRT. A tomotherapy machine is a hybrid between a CT imaging scanner and an external-beam radiation therapy machine (6). The part of the tomotherapy machine that delivers radiation for both imaging and treatment can rotate completely around the patient in the same manner as a normal CT scanner.
Stereotactic radiosurgery: Stereotactic radiosurgery (SRS) can deliver one or more high doses of radiation to a small tumor (5, 8). SRS uses extremely accurate image-guided tumor targeting and patient positioning. Therefore, a high dose of radiation can be given without excess damage to normal tissue.
Stereotactic body radiation therapy: Stereotactic body radiation therapy (SBRT) delivers radiation therapy in fewer sessions, using smaller radiation fields and higher doses than 3D-CRT in most cases. By definition, SBRT treats tumors that lie outside the brain and spinal cord. Because these tumors are more likely to move with the normal motion of the body, and therefore cannot be targeted as accurately as tumors within the brain or spine.
Proton therapy: External-beam radiation therapy can be delivered by proton beams as well as the photon beams described above. Protons are a type of charged particle.
Other charged particle beams: Electron beams are used to irradiate superficial tumors, such as skin cancer or tumors near the surface of the body, but they cannot travel very far through tissue (1). Therefore, they cannot treat tumors deep within the body.
Internal radiation therapy
Internal radiation therapy (brachytherapy) is radiation delivered from radiation sources (radioactive materials) placed inside or on the body . Several brachytherapy techniques are used in cancer treatment. Interstitial brachytherapy uses a radiation source placed within tumor tissue, such as within a prostate tumor. Intracavitary brachytherapy uses a source placed within a surgical cavity or a body cavity, such as the chest cavity, near a tumor. Episcleral brachytherapy, which is used to treat melanoma inside the eye, uses a source that is attached to the eye.
In brachytherapy, radioactive isotopes are sealed in tiny pellets or “seeds.” These seeds are placed in patients using delivery devices, such as needles, catheters, or some other type of carrier. As the isotopes decay naturally, they give off radiation that damages nearby cancer cells.
- For permament brachytherapy, the sources are surgically sealed within the body and left there, even after all of the radiation has been given off. The remaining material (in which the radioactive isotopes were sealed) does not cause any discomfort or harm to the patient. Permanent brachytherapy is a type of low-dose-rate brachytherapy.
- For temporary brachytherapy, tubes (catheters) or other carriers are used to deliver the radiation sources, and both the carriers and the radiation sources are removed after treatment. Temporary brachytherapy can be either low-dose-rate or high-dose-rate treatment.
Systemic Radiation Therapy
Systemic radiation therapy is a type of radiation therapy in which radioactive material travels through the bloodstream to reach cells all over the body. Systemic radiation is used to treat certain types of cancer, such as thyroid cancer, or to relieve pain when cancer has spread (metastasized) to the bone.