Internal mammary nodal irradiation in conservatively-managed breast cancerpatients: Is there a benefit?

Purpose: Recent randomized trials have demonstrated a significant benefit t o postmastectomy radiation in node-positive breast cancer patients. The con tribution of internal mammary nodal radiation (IMNR) to this benefit remain s controversial, and in conservatively-treated patients (CS + RT), may comp romise cosmesis and contribute to morbidity. The purpose of this retrospect ive analysis is to evaluate outcome as a function of IMNR in a cohort of br east cancer patients treated with CS + RT. Patients and Methods: Between January 1970 and December 1990, 984 patients with invasive breast cancer were treated at our facility with CS + RT, and serve as the base for this study. Of these patients, 399 patients had patho logically-negative lymph nodes, 167 (17%) had pathologically-involved lymph nodes, and 381 did not undergo lymph node dissection. The majority of node -positive patients received adjuvant systemic therapy (94%) and were treate d with tangential fields matched to a separate supraclavicular field (95%) with or without IMNR. For this analysis, patients were divided into two gro ups: those treated by intentionally targeting the internal mammary nodes (I M-yes, n = 535) and without intentionally targeting the internal mammary no des (IM-no, rt 411). In the IM-no group, the medial border was typically pl aced at midline. The decision not to use a separate internal mammary field was a result of a change in treatment policy over time, and generally not b ased on number of nodes or tumor location. Results: As of August 1998, with a median follow-up of 13 years, the overal l survival at 10 years is 76%, the distant disease-free survival is 81%, an d the breast relapse-free survival is 88%. There were no significant differ ences between the IRI-yes and IM-no groups with respect to age, ER/PR statu s, or use of adjuvant chemotherapy or hormone therapy. There were more pati ents with T2 tumors, positive nodes, medial lesions, indeterminate margins, and slightly longer follow-up in the IM-yes group compared to the IR;I-no group. Although there was a trend toward better outcome in the IM-no group, there were no significant differences between the IM-yes and LM-no groups with respect to overall survival (72% IM-yes vs. 84% IM-no, p = NS) or dist ant metastasis-free survival (64% IM-yes vs. 82% IM-no, p = NS). Subset ana lysis showed no benefit in the IM-yes group regardless of age, number of no des, or location. Conclusion: In this retrospective analysis, no benefit could be attributed to IMNR in conservatively-treated breast cancer patients, even if node-posi tive or medial in location. Until results of an ongoing EORTC randomized tr ial addressing this issue are available, these data suggest that it is acce ptable to continue to treat node-positive conservatively-managed patients t o tangential fields usually matched to a supraclavicular field, but without a separate internal mammary field. (C) 1999 Elsevier Science Inc.