(ChemotherapyAdvisor) – Compared to whole-breast irradiation, accelerated partial breast irradiation (APBI) using 3-D conformal external beam radiotherapy (3-D CRT) is associated with a higher rate of fibrotic distortions and poor cosmetic outcomes (“cosmesis”) for breast-conserving surgery among breast cancer patients, according to a randomized study presented at the American Society for Radiation Oncology’s (ASTRO’s) 54th Annual Meeting, Boston, MA.

“In patients who have undergone breast-conserving therapy, APBI delivered by 3D CRT was associated with worse cosmetic outcome and late radiation changes at 3 years compared with WBI,” reported lead author Timothy J. Whelan, MD, a radiation oncologist at the Juravinski Cancer Center in Hamilton, Ontario, Canada, and coauthors.

“Women with early-stage breast cancer who undergo breast-conserving surgery may be offered accelerated partial breast irradiation as part of their treatment,” Dr. Whelan noted. “Our study supports earlier phase 2 trial research and found that APBI using 3-D external beam radiation therapy can increase the risk of moderate radiation side effects, which may affect cosmetic outcome for some patients.”

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The study involved 2,135 women older than age 40 years with breast tumors less than 3 cm and treated with breast-conserving therapy during 2006 to 2011. Patients were randomized to receive 3D CRT APBI (38.5 Gy in 10 fractions, twice daily) or WBI (50 Gy in 25 fractions, once daily, or 42.5 Gy in 16 fractions, once daily) with or without boost irradiation, the authors reported.

The rate of adverse cosmesis at 3 years was significantly higher among patients who had undergone APBI than those receiving WBI (P <0.0001), whether assessed by the patients (26.2% vs 18.4%;P=0.004) or oncologists (35.1% vs 16.6%, P <0.0001), the authors reported.

Cosmetic outcomes were assessed by patients and oncologists, who provided “similar assessments in the rate of adverse cosmesis with APBI vs WBI,” the authors wrote.

Grade 1 and 2 toxicities, including breast induration, were more frequent in APBI-arm patients than patients receiving WBI, but grade 3 and 4 adverse reactions were “rare in both groups,” the authors reported.