Breast conservation therapy: the influence of molecular subtype and margins

To evaluate treatment results and prognostic factors, especially margin status and molecular subtype, in early-stage breast cancer patients treated with breast conservation therapy (BCT).

The records of 1,058 Stage I or II breast cancer patients treated with BCT (surgical excision plus radiotherapy) at Duke University Medical Center, Durham, North Carolina, from 1985-2005 were retrospectively reviewed. Conventional receptor analyses were used as surrogate markers for molecular subtype classification (luminal A, luminal B, Her2 positive, and basal like). Actuarial estimates of overall survival (OS), cause-specific survival (CSS), failure-free survival, and locoregional control (LRC) were computed by use of Kaplan-Meier plots. We analyzed prognostic variables for significance using Cox proportional hazards univariate and multivariate analysis. The study was approved by the Duke University Medical Center Institutional Review Board.

The median age of the patients was 56 years (range, 18-89 years). Of the patients, 80% had T1 disease and 66% N0 disease pathologically. With a median follow-up of 9.8 years, an in-breast recurrence developed in 53 patients and 10 patients had nodal failure. For all patients, the 10-year CSS rate was 94%; LRC rate, 94%; and failure-free survival rate, 88%. Luminal A patients had a CSS rate of 95% and LRC rate of 99%. Basal-type patients appeared to do worse, with regard to both CSS rate (74%) and LRC rate (76%), but the numbers were small and the difference was not statistically significant. LRC rates of patients with negative margins (widely negative, close, and extent of margin not known) were virtually identical (93%, 96%, and 94%, respectively). Those with positive margins appeared to fare slightly worse based on LRC rate (88%), but again, the numbers were small and the difference was not statistically significant.

BCT remains the treatment of choice for early-stage breast cancer patients irrespective of molecular subtype. Negative margins of excision are desirable, but the width of the negative margin does not influence outcome.