OPAR: A Randomized Trial of Partial Breast Irradiation in Five Fractions Once Daily for Early Breast Cancer
Mené sur 142 patientes atteintes d'un cancer du sein invasif ou d'un carcinome canalaire in situ d'une taille inférieure ou égale à 3 cm (âge : au moins 50 ans ; durée médiane de suivi : 5 ans), cet essai randomisé évalue les effets indésirables esthétiques de deux schémas d'irradiation partielle quotidienne du sein par faisceau externe (30 Gy ou 27,5 Gy) en cinq fractions
Résumé en anglais
PURPOSE: Previous studies suggest that external-beam partial breast irradiation (PBI) delivered twice a day can lead to increased adverse cosmesis (AC). The objective of our trial was to determine whether two regimens for PBI given once daily over 1 week resulted in acceptable AC to inform a phase III trial.
METHODS: Patients age ≥50 years with invasive breast cancer or ductal carcinoma in situ, ≤3 cm in size treated by lumpectomy with negative axillary nodes were randomly assigned to external-beam PBI of 30 Gy or 27.5 Gy, each given in five fractions once daily. The primary outcome was AC (fair or poor) by photographic assessment at 2 years. Secondary outcomes included AC assessed by nurse at 2 years, by patient self-assessment at 3 years, and late toxicity. On the basis of a 17% risk of AC with whole-breast irradiation, the upper bound of a two-sided 90% CI, 23% was set as the tolerance margin (OPAR, ClinicalTrials.gov identifier: NCT02637024).
RESULTS: In total, 142 patients were randomly assigned to 30 Gy and 139 to 27.5 Gy. The median follow-up was 5 years. The mean age was 65 years, and the mean tumor size was 1.2 cm. Both schedules met acceptability criteria by photographic assessment (AC, 12.1% [90% CI, 8.2 to 17.6] for 30 Gy and 15.2% [90% CI, 10.8 to 21.1] for 27.5 Gy) and by nurse assessment. AC by patient self-assessment exceeded the 90% CI for the 30 Gy regimen. At 5 years, 16 (11.3%, 90% CI, 7.6 to 16.4) patients treated with 30 Gy and eight (5.8%, 90% CI, 3.3 to 9.9) patients treated with 27.5 Gy were observed to have grade 2 or more late toxicity.
CONCLUSION: 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.
