Second malignancies after treatment of early-stage breast cancer: lumpectomy and radiation therapy versus mastectomy.

PURPOSE: To determine the risk of second malignancies after lumpectomy and radiation therapy (LRT), and to compare it with that in a similar cohort of early-stage breast cancer patients undergoing mastectomy without radiation (MAST). PATIENTS AND METHODS: Between January 1970 and December 1990, 1,029 breast cancer patients at our institution underwent LRT. A cohort of 1,387 breast cancer patients who underwent surgical treatment by mastectomy (MAST), and who did not receive postoperative radiation during the same time period, served as a comparison group. Second malignancies were categorized as contralateral breast versus nonbreast. In the cohort of patients undergoing LRT, a detailed analysis was carried out with respect to age, disease stage, smoking history, radiation therapy technique, dose, the use of chemotherapy or hormone therapy, and other clinical and/or pathologic characteristics. RESULTS: As of March 1999, the median follow-up was 14.6 years for the LRT group and 16 years for the MAST group. The 15-year risk of any second malignancy was nearly identical for both cohorts (17.5% v 19%, respectively). The second breast malignancy rate at 15 years was 10% for both the MAST and LRT groups. The 15-year risk of a second nonbreast malignancy was 11% for the LRT and 10% for the MAST group. In the subset of patients 45 years of age or younger at the time of treatment, the second breast and nonbreast malignancy rates at 15 years were 10% and 5% for patients undergoing LRT versus 7% and 4% for patients undergoing mastectomy (P, not statistically significant). In the detailed analysis of LRT patients, second lung malignancies were associated with a history of tobacco use. There were fewer contralateral breast tumors in patients undergoing adjuvant hormone therapy, although this did not reach statistical significance. The adjuvant use of chemotherapy did not significantly affect the risk of second malignancies. CONCLUSION: There seems to be no increased risk of second malignancies in patients undergoing LRT using modern techniques, compared with MAST. Continued monitoring of these patient cohorts will be required in order to document that these findings are maintained with even longer follow-up periods. With nearly 15 years median follow-up periods, however, these data should be reassuring to women who are considering LRT as a treatment option.