Prostate Cancer

The ability of radiation treatment to control prostate cancer depends on the total dose of radiation delivered. However, because of the risk of inducing side effects in the bladder and rectum, an imprecise dose is often given in conventional radiation treatment of prostate cancer. Unlike conventional radiation, proton radiation has a well-defined high-dose area, which can be manipulated to surround an irregularly shaped target such as the prostate gland. This advantage of protons allows physicians to deliver low doses to the bladder and rectum while high doses are delivered to the prostate.

In later stages of prostate cancer, the patient may have "nests" of prostate cancer cells within the pelvic lymph nodes. For these cancers, x-rays can be used to treat the lymph nodes in the pelvic field. Meanwhile, protons can be used to "boost" the levels of radiation at sites of gross disease. X-radiation alone may control the microscopic growths in the lymph nodes but an insufficient dose may be delivered to the primary cancer. Similarly, proton radiation alone may control the primary cancer, but the nodes distant from the primary cancer may not be irradiated sufficiently. In some cases, the solution is to use combined proton and x-ray treatment.

These approaches have been used at Loma Linda University Medical Center to treat several thousand patients with prostate cancer. Results show that proton radiation yields impressive outcomes in both early and locally more advanced cases. Proton radiation therapy improves biochemical disease-free control rates by at least 10 percent over conventional radiation therapy and reduces side effects by more than 10 percent. A randomized trial has demonstrated that the higher total dose made possible by protons results in a higher biochemical disease-survival rate, with no increase in radiation-related complications.

Chordomas and Chondrosarcomas

Chordomas and chondrosarcomas may arise at several sites. They impinge upon the brain stem or spinal cord and can invade central nervous system tissue. Proton radiation therapy has long been used to treat these tumors because it can deliver a high dose while avoiding brain or spinal cord tissues. Control rates with protons are much higher than for conventional radiotherapy in these regions, such as the base of the skull, where surgery is difficult because of the intimate association with central nervous system tissue.