Cancer treatment is individualized

Dear Dr. Roach: I read your recent column on prostate cancer treatments, and I must disagree on the differences between IMRT and proton radiation therapy. IMRT or X-rays can cause secondary aggressive cancers of the bowels or bladder. I know of an individual who died from this type of cancer after IMRT. Proton radiation therapy does not cause secondary cancers because of the way protons work. Secondary cancers due to IMRT occur in about 8 percent of patients. This may be acceptable odds for radiation oncologists, but not to patients who develop them. — M.D.

I always appreciate hearing differing opinions from my own, and here is why I disagree. The lifetime risk of a second malignancy after IMRT (now considered standard radiation treatment) for prostate cancer has been estimated to be about 1 person in 220 in all patients, but as high as one person in 70 (about 1.5 percent) among those who are followed over 10 years — 1.5 percent is much less than the 8 percent you quote. Proton therapy should have a decreased risk of secondary malignancy, but that is unproven. While early reports suggest that the risk of secondary malignancy in proton therapy may be about half the risk seen in traditional IMRT, proton therapy clearly does have an increased risk of secondary malignancy. Given a lack of proof of improved efficacy of proton therapy in survival in prostate cancer, and increased GI toxicity among proton-beam-treated patients, I reaffirm my recommendation that there is not yet a compelling reason to choose proton treatment over IMRT. That may change as further data accrues and as we learn how best to use proton treatments. I hope that the information in this column can enhance the discussion between a man with his doctor about the right treatment for them.