Internal mammary node irradiation improves overall survival in patients with early-stage node-positive breast cancer, a new study published online ahead of print in the Journal of Clinical Oncology has shown.1
Even if irradiation of the internal mammary lymph nodes improves survival in patients with early-stage breast cancer, that potential survival benefit may be offset by radiation-induced heart disease. Therefore, researchers sought to evaluate the effect of internal mammary node irradiation in patients with early-stage node-positive breast cancer.
For the nationwide, prospective population-based cohort study, researchers in Denmark analyzed data from 3089 patients who underwent surgery for unilateral early-stage node-positive breast cancer. Of those, 1492 had right-sided disease and were assigned to receive internal mammary node irradiation due to the risk of radiation-induced heart disease.
Results showed that after a median follow-up of 8.9 years, the 8-year overall survival rates were 75.9% with irradiation compared with 72.2% without it (HR, 0.82; 95% CI, 0.72 – 0.94; P = .005).
Researchers found that breast cancer mortality was 20.9% and 23.4% in the irradiation and no irradiation groups, respectively (HR, 0.85; 95% CI, 0.73 – 0.98; P = .03), and the risk of distal recurrence at 8 years was 27.4% and 29.7%, respectively (HR, 0.89; 95% CI, 0.78 – 1.01; P = .07).
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The study also demonstrated a more pronounced effect from internal mammary node irradiation in patients at high risk for developing internal mammary node metastasis.
In regard to safety, the same number of patients in each group died of ischemic heart disease.
- Thorsen LBJ, Offersen BV, Danø H, et al. DBCG-IMN: a population-based cohort study on the effect of internal mammary node irradiation in early node-positive breast cancer [published online ahead of print November 23, 2015]. J Clin Oncol. doi: 10.1200/JCO.2015.63.6456.