Radiation Oncology 101

At least 50% of all cancer patients receive radiation therapy at some stage during the course of their treatment. This type of cancer therapy uses targeted doses of high-energy radiation to kill cancer cells in the body. As technology advances, radiation oncology is becoming more precise in targeting cancer sites ultimately leading to better patient outcomes. It is important to understand the different types of radiation therapy to stay informed on your treatment plan .

Types of Radiation Therapy

• Conformal Radiation Therapy (CRT) uses Computed Tomography (CT) images and planning computers to precisely map the location of a tumor in three dimensions. CRT is delivered by a machine called a linear accelerator that generates high-energy x-ray beams that are precisely aimed at the tumor from multiple directions. By mapping the shape of the tumor, radiation oncologists can more accurately target specific cancer sites while avoiding healthy tissue.
• Intensity-Modulated Radiation Therapy (IMRT) is similar to CRT, but along with aiming beams from multiple directions, the intensity (strength) of the beams can be modified. This gives clinicians the ability to further control the radiation, delivering high doses only to the cancerous tissue while sparing the surrounding healthy tissues.
• Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT) are techniques used to deliver a large radiation dose to a small tumor with extreme precision in a small number of treatments. A linear accelerator, or special machines such as the Gamma Knife¨ or CyberKnife¨, can be utilized to deliver this type of treatment.
• Brachytherapy uses radioactive sources that are placed directly within or adjacent to the cancer site. By placing the source in close proximity to the tumor, physicians can minimize the dose to surrounding healthy tissues. Brachytherapy is commonly used as a treatment for many cancers including prostate, breast, skin, and gynecological cancers.
• Selective Internal Radiation Therapy (SIRT) is a type of radiation therapy that is delivered in collaboration with interventional radiologists typically for the treatment of liver cancer. In these treatments, radioactive microspheres are injected directly into the arteries supplying the liver tumors, providing a high dose to the tumor while minimizing the dose to the surrounding healthy liver tissues.
• Intraoperative Radiation Therapy (IORT) is a form of treatment which delivers radiation at the time of surgery. The radiation can be targeted directly at the cancer site or to the nearby tissues after the cancer has been removed. It's commonly used in breast, abdominal and pelvic cancers and in cancers with high probability of recurrence. IORT minimizes the amount of tissue exposed to radiation because normal tissues can be moved out of the way during surgery and shielded.
• Proton Beam Radiation Therapy uses beams of positively charged particles rather than conventional high-energy x-ray beams. The potential benefit of proton therapy is that proton beams target radiation dose to very specific depths within the body, thereby reducing the radiation delivered to the tissues surrounding the tumor.

The Current Role of Proton Therapy in Treating Cancer

The widespread use of proton therapy to treat cancerous tumors is still in its early stages but proton therapy has shown potential benefits as a radiation therapy option. Proton beams have shown promise in treating large ocular melanoma tumors, pediatric central nervous system cancers, and may also be used in treating prostate and gastrointestinal cancers. Clinical data is still under investigation and insufficient to suggest that the outcomes of proton therapy are better than those of x-ray therapy.

The Future of Proton Therapy

Proton therapy research continues as oncologists and researchers explore the outcomes of the treatment option and weigh benefits. The necessary equipment for proton therapy is significantly larger than most radiation therapy machines and the treatment is expensive, though efforts are being made to develop a more cost-effective alternative.

In the U.S., there are currently 14 operational proton therapy centers, 10 under construction, 21 under development, and 2 being built in the UK. In the Nashville community, the Scott Hamilton Proton Center announced a new site in Franklin, Tenn. This new site will provide access to novel proton therapies to cancer patients in the region.

Sources:
Varian- Proton Therapy
Nashville Business Journal
Wall Street Journal