Same Survival and Toxicity With APBI and WBI for Breast Cancer

Accelerated partial breast irradiation (APBI) leads to the same rates of survival and toxicity as whole breast irradiation (WBI) while also producing significantly better cosmetic results, according to phase 3 trial results presented at European Society for Therapeutic Radiotherapy and Oncology (ESTRO) 35 (April 29-May 3, 2016; Turin, Italy).

Both APBI and WBI are part of breast conservation therapy, but whereas WBI exposes more of the breast to radiation and can require daily treatments for 3-7 weeks, APBI delivers radiation directly to the tumor bed and requires significantly less treatment time. This has made it an attractive treatment option for clinicians treating patients with breast cancer.

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In earlier results of the GEC-ESTRO (APBI Versus EBRT Therapy After Breast Conserving Surgery for Low-risk Breast Cancer) trial, published last year in Lancet, APBI already demonstrated equivalent rates of overall survival, disease-free survival, and local and regional cancer control when compared with traditional WBI with boost after breast conserving surgery. Additional findings presented by Csaba Polgár MD, PhD, MSc, National Institute of Oncology (Budapest, Hungary), at ESTRO 35 provided added insight into late side effects and cosmetic results.

For the trial, 1184 patients with breast cancer were randomly assigned to receive WBI with boost (n = 551) or APBI with interstitial multicatheter brachytherapy (n = 633). All participants were aged 40 years or older, and the median follow-up was 6.6 years.

At  5-year follow-up, 969 patients (82%) were available for review. Rates of grade 2-3 late skin toxicity were 5.7% with WBI and 3.2% with APBI; subcutaneous tissue effects were 6.3% with WBI and 7.6% with APBI; severe (grade 3) fibrosis were 0.2% with WBI and 0% with APBI; and grade 2-3 breast pain were 3.2% with WBI and 1.4% with APBI.

The rates of excellent or good cosmetic results were also similar between the two groups when judged by patients (87.2% with WBI vs 90.4% with APBI) and by physicians (86.7% with WBI vs 88.2% with APBI). However, significantly more patients experienced excellent cosmetic results in the APBI group than in the WBI group (43.6% vs 30.9%).

"APBI with interstitial multicatheter brachytherapy offers a significantly shorter treatment course with equivalent local tumor control, less late skin side effects, and better cosmetic results compared to conventional WBI," concluded Dr Polgár.

These findings add to the growing evidence base supporting APBI treatment for the treatment of early-stage breast cancer.