Risk of second malignancies after adjuvant radiotherapy for breast cancer: a large-scale, single-institution review.

Purpose: The aim of this study was to estimate the risk of second malignancies (SM) after radiation therapy (RT) for breast cancer (BC) in a large, institutional, homogeneous cohort of patients.

Methods And Materials: We retrospectively studied 16,705 patients with nonmetastatic BC treated at the Institut Curie in Paris between 1981 and 1997. Adjuvant RT was given to 13,472 of these patients, and no RT was given to 3,233. The SM included all first nonBCs occurring during follow-up. Cumulative risks for each group were calculated using Kaplan-Meier estimates, censoring for contralateral cancer or death.

Results: Median patient age at diagnosis of BC was 55 years for the whole population, and 53 and 60 years for patients who had and had not undergone irradiation, respectively. At the 10.5-year median follow-up, 709 patients were diagnosed with SM (113 in the non-RT and 596 in the RT group). There was a significant increase in the rate of sarcomas and lung cancers in the RT group compared with non-RT group (p 0.02). Treatment with RT was not found to increase the risk of other types of cancers such as thyroid cancer, malignant melanoma, gastrointestinal or genitourinary, and hematologic SM.

Conclusions: This study suggests that adjuvant RT increased the rate of sarcomas and lung cancers, whereas it did not increase the rate of other malignancies.