As reported in the Journal of Clinical Oncology by Meduri et al, a 5-year analysis from the phase III IRMA trial has shown higher rates of adverse cosmesis and some late toxicities with external-beam accelerated partial-breast irradiation (APBI) vs whole-breast irradiation (WBI) in women with stage I to IIA breast cancer undergoing breast-conserving surgery.
In the trial, 3,225 patients aged ≥ 49 years from sites in five European countries were randomly assigned between March 2007 and March 2019 to receive external-beam radiation therapy with APBI (n = 1,602) or WBI (n = 1,623). WBI consisted of a total dose of 50 to 50.4 Gy/25 to 28 fractions, 42.56 Gy/16 fractions, 45 Gy/18 fractions, or 40 Gy/15 fractions, according to the practice of study centers. The prescribed APBI dose was 38.5 Gy in 10 fractions given twice daily over 5 days.
The primary endpoint of the trial is ipsilateral breast cancer recurrence. Outcomes have yet to be reported.
Median follow-up was 5.6 years (interquartile range = 4.0–8.4 years). Overall survival at 5 years was 97.4% (95% confidence interval [CI] = 96.5%–98.1%) in the APBI group and 97.2% (95% CI = 96.2%–97.9%) in the WBI group. Adverse cosmesis was reported by 12.7% of patients in the APBI group vs 9.2% of the WBI group at 3 years (P = .009) and by 14% vs 9.8% at 5 years (P = .012).
The cumulative risk of grade 3 to 4 late soft-tissue toxicity at 5 years was 2.8% in the APBI group vs 0.9% in the WBI group (P < .001). The cumulative 5-year risk for grade ≥ 3 late bone toxicity was 1.2% in the APBI group vs 0% in the WBI arm (P < .001). No significant differences between the APBI group vs the WBI group were observed in risk for late grade ≥ 3 skin toxicity (0.5% vs 0.4%) or late grade ≥ 3 lung toxicity (0.1% vs 0.2%).
The investigators concluded, “External-beam radiation therapy-APBI with a twice-daily IRMA schedule was associated with increased rates of late moderate soft-tissue and bone toxicities, with a slight decrease in patient-reported cosmetic outcomes at 5 years when compared with WBI, although overall toxicity was in an acceptable range.”
Bruno Meduri, MD, of the Department of Radiation Oncology, University Hospital of Modena, Italy, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Italian Ministry of Health and the Regional Authority for Health Policies of Emilia-Romagna and the Dutch Cancer Society. For full disclosures of the study authors, visit ascopubs.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.