Amsterdam, The Netherlands—Expanded radiotherapy led to significantly better disease-free survival (DFS) and metastasis-free survival (MFS) rates in women with early breast cancer, according to the results of a large study reported at the European Cancer Congress 2013.
Irradiation of the internal mammary and medial supraclavicular lymph nodes was associated with a 10-year DFS rate of 72.1% compared with 69.1% in patients with stage I to III breast cancer. An identical absolute difference of 3% was observed in favor of expanded irradiation for MFS. The 10-year overall survival (OS) favored expanded radiotherapy.
“Our results make it clear that irradiating these lymph nodes gives a better patient outcome than giving radiation therapy to the breast and thoracic wall only,” Philip Poortmans, MD, PhD, Radiation Oncologist, Instituut Verbeeten, Tilburg, The Netherlands. “Not only have we shown that such treatment has a beneficial effect on locoregional disease control, but it also improves distant metastasis-free survival and overall survival.”
The results addressed a long-standing debate about the potential benefits of irradiating secondary lymphatic pathways after surgery for early breast cancer. Although irradiation of axillary lymph nodes has become standard practice, the need to treat the internal mammary nodes and the supraclavicular nodes remained unresolved.
This randomized trial was conducted at 43 European centers and involved 4000 patients with newly diagnosed stage I to III breast cancer. Approximately 75% of the patients had breast-conserving surgery, and 85% of those had a radiation boost to the primary tumor bed. Among patients who underwent mastectomy, 75% received chest wall irradiation.
The patients were randomized to expanded radiotherapy that included the internal mammary and medial supraclavicular lymph nodes or to standard radiotherapy limited to the axillary lymph nodes. The primary end point was OS, and the trial had the power to detect an improvement in 10-year OS from 75% to 79%.
After a median follow-up of 10.9 years, the results showed a trend toward better OS with irradiation of the secondary lymphatic pathway, but the difference did not achieve significance (82.3% vs 80.7%; P = .056).
“The lack of a significant difference in overall survival can be explained by the better-than-expected survival among patients who received standard irradiation,” said Dr Poortmans.
Irradiation of the internal mammary and supraclavicular nodes was associated with significant improvement in DFS (P = .044) and in MFS (78% vs 75%; P = .020). The benefits of expanded irradiation did not vary by the number of involved lymph nodes, Dr Poortmans reported. The stage at diagnosis also did not affect the beneficial effect.“This is likely to be related to the positive interaction of the [radiation] treatment with systemic treatment—chemotherapy, hormonal therapy, and targeted therapy,” Dr Poortmans said.
These investigators had previously reported that additional exposure to radiotherapy did not significantly increase the incidence of adverse events.