Lymphoscintigraphy Can Select Breast Cancer Patients for Internal Mammary Chain Radiotherapy

Purpose: Given the risk of undesired toxicity, prophylactic internal mammary (IM) chain irradiation should be offered only to patients at high risk of occult involvement. Lymphoscintigraphy for axillary sentinel node biopsy might help in selecting these patients. Methods and Materials: We reviewed published studies with the following selection criteria: ≥300 breast cancer patients referred for axilla sentinel node biopsy; scintigraphy performed after peritumoral or intratumoral tracer injection; IM biopsy in the case of IM drainage; and axilla staged routinely independent of IM status. Results: Six prospective studies, for a total of 3,876 patients, fulfilled the inclusion criteria. Parasternal drainage was present in 792 patients (20.4%). IM biopsy was performed in 644 patients and was positive in 111 (17.2%). Of the positive IM biopsies, 40% were associated with tumors in the lateral breast quadrants. A major difference in the IM positivity rate was found according to the axilla sentinel node status. In patients with negative axilla, the IM biopsy was positive in 7.8% of cases. In patients with positive axilla, however, the IM biopsy was positive in 41% (p < .00001). Because biopsy of multiple IM hot nodes is difficult, the true risk could be even greater, probably close to 50%. Conclusions: Patients with IM drainage on lymphoscintigraphy and a positive axilla sentinel node have a high risk of occult IM involvement. These women should be considered for IM radiotherapy.