ASTRO 2021: Accelerated Partial-Breast Irradiation Fractions and Breast Cosmesis
Posted: Monday, November 15, 2021
Do-Hoon Kim, MD, of McMaster University-Juravinski Cancer Centre, Hamilton, Ontario, Canada, and colleagues conducted the multicenter, phase II OPAR trial to establish whether two doses of accelerated partial-breast irradiation given once a day for 1 week would result in “acceptable” long-term morbidity. Presented during the 2021 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 9), their results concluded that both 27.5 Gy and 30.0 Gy of radiation produced acceptable outcomes, although the lower fraction may prove to be preferred in terms of late adverse effects.
A total of 281 patients with ductal carcinoma in situ or invasive breast cancer were randomly assigned to receive either 27.5 Gy (n = 139) or 30.0 Gy (n =142) of accelerated partial-breast irradiation in five fractions once per day, for 5 to 8 days. Cosmetic evaluation was performed at baseline and at 2 years by both oncologists and a nurse as well as at 3 years by patients.
The median follow-up was 3 years, with a mean tumor size of 1.2 cm. Compared with 30.0 Gy, 27.5 Gy appeared to induce less adverse cosmesis, according to both the nurse at 2 years (12.9% vs. 7.7%) and the patients at 3 years (20.9% vs. 11.8%). Additionally, the rate of cosmetic deterioration was found to be lower among patients receiving 27.5 Gy versus 30.0 Gy at 2 years (5.6% vs. 7.6%).
Considering the upper bound of the confidence interval had to be less than 23% for treatment to be considered acceptable, both 27.5 Gy and 30.0 Gy fractions were deemed to be adequate. No local recurrence was observed with 27.5 Gy, and one case of local recurrence was observed with 30.0 Gy. However, 4.9% of individuals receiving 30.0 Gy experienced late toxicity, whereas 1.4% of those given 27.5 Gy did.
Disclosure: The study authors reported no conflicts of interest.
