RADIATION AFTER PROSTATECTOMY AND RISK OF SECOND CANCERS

NEW YORK (Reuters Health) Oct 15 - Radiation therapy after radical prostatectomy slightly increases the risk of developing a second primary cancer in the pelvic region that received some or all of the radiation dose, according to a report in the October Urology.

"This paper is re-assuring, rather than alarming, because it demonstrates that the risk of radiation-induced malignancy is extremely low and...that the long-feared radiation therapy-induced second primary cancer is insignificant compared to the overall risk of second primary cancers from other causes in patients with prostate cancer," Dr. May Abdel-Wahab from University of Miami, Florida told Reuters Health by email.

Dr. Abdel-Wahab and her colleagues investigated the incidence of second primary cancers and late radiation-induced second primaries after radical prostatectomy alone or with radiotherapy, using data from the Surveillance, Epidemiology, and End Results (SEER) registry from 1988 to 2002.

Overall during that period, 228,235 men were diagnosed with local/regional prostate adenocarcinoma as their first malignancy. Of this group, 80,157 were treated with radical surgery alone, and 5,044 underwent radical surgery plus radiation therapy.

For the entire cohort, after 5 more years with prostate cancer, the frequency of second primary cancers was 8.4%, including 3101 cases in pelvic organs and areas that would receive most or all of a radiation dose (that is, the bladder, rectum, anus or anal canal, prostate, soft tissue, bones and joints). An additional 552 second primaries developed in pelvic regions that might receive some radiation (including the rectosigmoid region, penis, small intestine, ureter, other urinary and male genital organs, and testes). Finally, there were 15,529 second primary cancers in nonpelvic areas.

Radiation therapy after radical surgery was associated with a statistically significant increase only in late second primaries occurring in the pelvic area that received the bulk of the radiation.

The most frequent pelvic second cancers were in the bladder (2303 cases) or the rectum or rectosigmoid junction (1006 cases). The most frequent non-pelvic second cancers were in the bronchus and lung (4131 cases), colon (2665 cases), and skin (1769 cases).

For the radical surgery only and the radical surgery plus radiation groups, the absolute risks of developing a second malignancy were 1581 and 1747 cases, respectively, per 100,000.

"The number of extra radiation therapy-induced malignancies is too small to affect survival or to attenuate the benefits of radiation therapy, which are much greater in magnitude," Dr. Abdel-Wahab concluded. "The benefits of radiation outweigh the risks."

In an editorial, Dr. Mark S. Soloway, also from the University of Miami, writes, "In my view, there is sufficient evidence that external beam radiation therapy in the doses used to treat adenocarcinoma of the prostate leads to a small but definite risk of in-field, and likely other, malignancies."

He adds, "I believe one should mention the risk, albeit small, of a radiation-induced second primary cancer" in conversations with patients.

Urology 2009;74:866-871,871-872.