In the Canadian phase II OPAR trial reported in the Journal of Clinical Oncology, Kim et al found no difference in adverse cosmesis with partial breast irradiation (PBI) in five daily fractions of 30 Gy vs 27.5 Gy given over 1 week in patients with early breast cancer. The aim of the trial was to determine whether the PBI schedules resulted in acceptable adverse cosmesis for evaluation in a phase III trial.
Study Details
In the multicenter trial, 281 patients were randomly assigned to receive 30 Gy (n = 142) or 27.5 Gy (n = 139). Patients were aged ≥ 50 years (median = 65 years) and had invasive breast cancer or ductal carcinoma in situ ≤ 3 cm treated by lumpectomy, with negative axillary nodes. The primary outcome measure was adverse cosmesis, defined as fair or poor by photographic assessment at 2 years. On the basis of a 17% risk of adverse cosmesis observed with whole-breast irradiation, the upper bound of the two-sided 90% confidence interval [CI] of 23% was defined as the tolerance margin.
Key Findings
Both schedules met acceptability criteria on photographic assessment at 2 years, with adverse cosmesis rates of 12.1% (90% CI = 8.2%–17.6%) in the 30-Gy group and 15.2% (90% CI = 10.8%–21.1%) in the 27.5-Gy group. Both schedules met acceptability criteria on nurse assessment at 2 years, with adverse cosmesis rates of 12.9% (90% CI = 8.8%–18.4%) in the 30-Gy group and 7.7% (90% CI = 4.7%–12.5%) in the 27.5-Gy group.
On patient self-assessment at 3 years, adverse cosmesis rates were 20.1% (90% CI = 13.6%–30.0%) in the 30-Gy group, not meeting acceptability criteria, and 13.0% (90% CI = 7.6%–21.4%) in the 27.5-Gy group. At 5 years, grade ≥ 2 late toxicity was observed in 11.3% of the 30-Gy group and 5.8% of the 27.5-Gy group.
The investigators concluded: “According to the study design, 30 Gy and 27.5 Gy resulted in acceptable cosmetic outcomes. In light of recent studies, a lower dose was chosen for the phase III trial.”
Timothy J. Whelan, BM, BCh, of McMaster University and Juravinski Cancer Centre at Hamilton Health Sciences, Ontario, is the corresponding author of the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Breast Cancer Research in Greater Hamilton Today Run and Canadian Breast Cancer Foundation. For full disclosures of the study authors, visit ascopubs.org.
