Contralateral breast cancer and other second malignancies in patients treated by breast-conserving therapy with...

Metachronous contralateral breast cancers and other second malignancies were evaluated in 2,850 patients treated between 1960 and 1981 primarily with radiotherapy (RT) either alone or following breast-conserving surgery. One hundred eighty-four contralateral cancers were observed in 22,491 patient-years of observation (818 per 10(5) patient-years), with a cumulative probability of 4.5% at 5, 7.9% at 10, and 11% at 15 and 20 years. Compared to patients with unilateral tumors, those destined to develop contralateral cancers were younger (mean age 51.9 vs 56.6) and more often gave a family history of breast cancer. Contralateral breast cancers were more frequent for more extensive tumors (T3 10% vs T1-26%; with inflammatory signs 10.6% without 6%), and in patients with ipsilateral local recurrence (with 9.1%, without 5.6%). Patients with contralateral cancers had a significantly less favorable survival experience (15-year actuarial survival after primary therapy 42%) than patients without contralateral cancer (15-year survival 65.5%). In early stage patients treated with conservative surgery and RT, contralateral cancer was not prognostically more favorable than ipsilateral breast recurrence. Among 72 other second malignancies (320 per 10(5) patient-years) were 2 soft tissue sarcomas in the irradiated area. This corresponds to an incidence of 21 cases per 10(5) patient-years for survivors beyond the fifth year. The possible influence of RT on contralateral cancers and other second malignancies is discussed.