Poortmans PM, Struikmans H, De Brouwer P, et al. - In stage I-III breast cancer patients with involved axillary nodes and/or a medially located primary tumor, statistically significantly higher incidence of late pulmonary side effects were observed, as were some of the cardiac events, in correlation with undergoing internal mammary and medial supraclavicular (IM-MS) lymph node irradiation.

• A total of 4,004 patients were accrued between 1996 and 2004 from 46 departments in 13 countries.

• At 15 years, cumulative incidence rates were 2.9% vs 5.7% for lung fibrosis, of 1.1% vs 1.9% for cardiac fibrosis, and of 9.4% vs 11.1% for any cardiac disease, when treated without or with IM-MS lymph node irradiation.

• No differences were observed between left- and right-sided breast cancer.

• At 15 years, the cumulative incidence probabilities of cross-sectionally reported side effects with a score of 2 or greater for pulmonary, cardiac and esophageal were 0.1% vs 0.8%, 1.8% vs 2.6%, and 0.0% vs 0.1%, respectively.