Doctors divide localized prostate cancer (prostate cancer that is only in the prostate gland and which has not spread outside of the prostate) into three risk groups. Low-risk prostate cancers are unlikely to grow or spread for many years. Medium-risk cancers are unlikely to grow or spread for a few years. High-risk cancers may grow or spread within a few years. Three criteria are generally used for classifying prostate cancer risk: PSA level, Gleason score, and T stage. PSA is a protein produced by both normal and cancerous prostate cells; a high level of PSA can be a sign of cancer. The Gleason score is a qualitative assessment of any cancer cells that may be present. T stage refers to the size and extension of tumors.

Radiation therapy is associated with side effects and those side effects have been shown to increase with radiation dose, said Kalbasi. For patients undergoing prostate radiation, side effects include, fatigue, urinary frequency and urgency, changes in bowel habits, and erectile dysfunction.


Prostate cancer is the most common cancer diagnosed among American men, and causes more deaths annually among men than any other tumor except lung cancer. However, a large majority of men found to have prostate cancer ultimately die of other causes, prompting researchers to conduct studies to identify who benefits most from treatment and what those treatments should be.

"Our findings show that the dose of radiation should be personalized to the specific characteristics of the prostate tumor," said Justin Bekelman, MD, an associate professor of Radiation Oncology at Penn, and the study's senior author. "For some patients, personalized treatment will lower the chances of toxicity while maintaining similar survival rates; for other patients, personalized treatment will mean escalating radiation dose to achieve the highest survival while protecting normal tissues, like the bladder and rectum."

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