Optimal Radiation Dose for Patients with One to Three Lymph Node Positive Breast Cancer Following Breast-Conserving Surgery and Anthracycline plus Taxane-Based Chemotherapy: A Retrospective Multicenter Analysis (KROG 1418)

Abstract

Background and Purpose

This study was performed to determine optimal radiation dose in pN1 breast cancer patients who received breast conserving surgery (BCS) and anthracycline plus taxane (AT)-based chemotherapy.

Materials and Methods

Retrospective chart reviews were performed in 1,147 patients who were treated between January 2006 and December 2010. The impact of radiation dose on treatment outcomes was evaluated.

Results

Median follow-up time was 66 months. The 5-year rate of disease-free survival (DFS) was 93.2%. Larger tumor size (> 20 mm), positive lymphovascular invasion, high histologic grade, and high ratio of positive nodes (> 0.1) were significantly associated with inferior DFS. By using the 4 factors related to DFS, patients were categorized into high-risk (with ≥ 3 factors) and low-risk (with < 3 factors) groups. In the high-risk group, higher radiation dose (> 60.3 GyEQD2) was significantly associated with better DFS than the lower dose (≤ 60.3 GyEQD2). However, the radiation dose did not impact DFS in the low-risk group.

Conclusions

Dosing of radiation affects the outcome of post-BCS radiotherapy in pN1 breast cancer. Doses of over 60.3 GyEQD2 were associated with better outcome in the high-risk patients.