Internal mammary nodal chain drainage is a prognostic indicator in axillary node-positive breast cancer.

Background: Internal mammary (IM) nodes are a potential site of breast lymphatic drainage. We examined the relationship between lymphoscintigraphic evidence of IM drainage and survival in early-stage breast cancer patients (pts).

Methods: From a prospective database of 855 consecutive sentinel node mapping procedures using peritumoral radiocolloid injection from 1996-2004, we analyzed the 604 cases with stage I-III breast cancer. Overall survival and recurrence-free survival (OS, RFS) rates were compared in pts with (IM+) and without (IM-) IM drainage on lymphoscintigraphy using Kaplan-Meier plots and Cox proportional hazards models.

Results: 100 of 604 pts (17%) showed IM drainage. Five-year OS and RFS were 92% vs 88% and 88% vs 85% in IM- vs IM+ pts. In the 186 pts with axillary metastases (node+), 5-year OS and RFS were 91% vs 71% and 84% vs 69% in IM- vs IM+ pts. Univariate analysis of node+ pts estimated increased mortality risk for IM+ (hazard ratio, HR 2.9, P = .04), >or=4 positive nodes (HR 3.2, P = .02), tumors that were ER-negative (HR 3.4, P = .02), or had high Ki-67 (HR 6.8, P = .01). Multivariate analysis estimated similar increased risks [>or=4 nodes (HR 4.0, P = .02), IM+ (HR 3.3, P = .06), and ER negativity (HR 2.6, P = .09)].

Conclusions: IM nodal drainage predicted a nearly 3-fold increased mortality risk in node+ pts. Peritumoral radiocolloid injection provides a clinically relevant assessment of IM drainage and should be prospectively tested for its value in tailoring treatment strategies for axillary node-positive pts.