Reply to Wilms tumor and breast cancer.

Malignant tumors are a well-documented late complication of therapy for Wilms tumor. Lange et al reported that female survivors of Wilms tumor who were treated with radiotherapy to the thorax at a dose of 12 to 14 gray (Gy) had an elevated risk of developing early breast cancer, with nearly 15% having invasive disease by age 40 years. Radiotherapy to the thorax is a risk factor for male breast cancer as well. Chest radiography does not increase the risk, but chest radiotherapy does. Moreover, in survivors of the atom bomb, this risk was found to be increased by a factor of 8. Therefore, we wondered whether men, as well as women, had an increased risk of breast cancer after a diagnosis of Wilms tumor and receipt of radiotherapy. Bassal et al calculated standardized incidence ratios from Surveillance, Epidemiology, and End Results (SEER) data and found that the risk of subsequent breast cancer in survivors of childhood cancer was 24.7. Using SEER data, we found that the risk of breast cancer was indeed elevated in women after a diagnosis of Wilms tumor and receipt of radiotherapy, but the risk of breast cancer in men was not. In the SEER data, 416 women had received beam radiotherapy. At 20 years of follow-up, 4 women had developed breast cancer, for an observed/expected (O/E) ratio of 7.4, which was significantly elevated (P <.05). Among 475 women who had not received beam radiotherapy, there were 2 cases of breast cancer, for an O/E ratio of 1.9, which was not significantly elevated. The elevation in the O/E ratio is not as great as reported by Lange et al, no doubt because SEER does not specify whether radiotherapy was given to the chest or abdomen. It is interesting to note that of the 372 men who had received beam radiotherapy, none had developed breast cancer, nor had any of the nonirradiated men shown signs of breast cancer. Low-dose radiation (3-23 Gy) is often given to men with prostate cancer who are receiving antiandrogen therapy to prevent gynecomastia, although the long-term effects are unknown. Our finding of no breast cancer in men after irradiation for Wilms tumor suggests that a dose of at least 14 Gy for the prevention of gynecomastia should be free of long-term effects.