Five-year toxicity profiles and cosmetic results were similar for patients with low-risk breast cancer who underwent breast-conserving surgery followed by either accelerated partial breast irradiation (APBI) with interstitial brachytherapy or conventional whole-breast irradiation, according to a study published in The Lancet Oncology.1

A previously reported phase 3 study confirmed the non-inferiority of APBI with interstitial brachytherapy compared with whole-breast irradiation for local control and overall survival among patients with early-stage breast cancer who underwent breast-conserving surgery. To further support these findings, researchers conducted an analysis of 5-year late side effects and cosmetic results of the study.

Median follow-up was 6.6 years. Less than 1% of the 484 evaluable patients who received APBI with interstitial multi-catheter brachytherapy and 2% of the 393 evaluable patients who underwent whole-breast irradiation had grade 3 late skin toxicity.

No patients in the APBI group and less than 1% of those in the whole-breast irradiation arm developed grade 3 late subcutaneous toxicity. No grade 4 toxicities were reported.

The cumulative incidence of any grade 2 or worse late side-effect at 5 years was 23.3% (19.9-26.8) in the APBI group vs 27.0% (95% CI, 23.0-30.9) in the whole-breast irradiation group.

Patients in the APBI group were less likely to develop grade 2 to 3 late dermatologic toxicity at 5 years. The cumulative incidence of grade 2 to 3 breast pain was not significantly different between the 2 groups.

Ninety-two percent of 541 patients in the APBI group and 91% of 454 patients in the whole-breast irradiation group reported excellent to good cosmetic results; similarly, 93% and 90%, respectively had excellent to good cosmetic results when judged by the physicians.

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For the phase 3 trial (ClinicalTrials.gov Identifier: NCT00402519), investigators enrolled 1328 women aged 40 years or older with stage 0-IIA breast cancer who underwent breast-conserving surgery with microscopically clear resection margins of at least 2 mm. Participants were randomly assigned 1:1 to receive whole-breast irradiation of 50 Gy with a tumor-bed boost of 10 Gy or APBI with interstitial multi-catheter brachytherapy.

These findings support the routine use of APBI with interstitial brachytherapy after breast-conserving surgery in low-risk breast cancer.

Reference

  1. Polgar C, Ott OJ, Hildebrandt G, et al. Late side-effects and cosmetic results of accelerated partial breast irradiation with interstitial brachytherapy versus whole-breast irradiation after breast-conserving surgery for low-risk invasive and in-situ carcinoma of the female breast: 5-year results of a randomised, controlled, phase 3 trial. Lancet Oncol. 2017 Jan 13. doi: 10.1016/S1470-2045(17)30011-6 [Epub ahead of print]