OT2-06-01: A Phase III Randomized Multicentric French Study To Evaluate the Impact of a Localized 16-Gy Boost after Conservative Surgery and a 50-Gy Whole-Breast Irradiation in Breast Ductal Carcinoma In Situ (The BONBIS Trial).

Background Ductal carcinoma in situ is defined as breast cancer confined to the ducts of the breast without evidence of penetration of the basement membrane. Local treatment quality represents one of the most prognostic factors as half of recurrences are invasive diseases. The main goal of adjuvant radiotherapy after conservative surgery is to decrease local recurrences and to permit breast conservation with low treatment-induced sequelae. Several randomized trials have established the impact of 50 Gy to the whole breast (WB) in terms of local control. Nevertheless, no randomized trial is still available concerning the role of the boost in this disease. The phase III randomized trial “BONBIS” is elaborated to evaluate the impact of a 16-Gy boost after 50 Gy delivered to the whole breast in 25 fractions and 33 days. Methods : A total of 1950 patients DCIS breast cancer patients are planned to be enrolled in this trial. Patients will receive the following treatment: (A) WB radiotherapy of 50 Gy in 25 fractions vs. (B) WB radiotherapy of 50 Gy in 25 fractions plus a localized 16-Gy boost in 8 fractions. The primary endpoint is local-relapse free survival (LRFS). This trial is designed to detect an expected rate in control arm of 7% and 4 % in experimental arm. With 90% power and a=0.05, 137 events are necessary to achieve the main goal. An interim analysis is planned after 50% of observed event. Stratifications are made based on recognized prognostic factors: age, hormonal treatment, differentiation, circumstance of diagnosis, surgical margin, centre. Secondary endpoints are relapse free survival, overall survival, acute and late toxicities, cosmetic results, and quality of life. Translational researches are also planned to identify intrinsic radiosensitivity of normal tissues (radiation-induced apoptosis assay, genome-wide association study) but also predictive models of tumor recurrences. Inclusions have started in November 2008 and are not so far than the planned estimation. This trial is granted by the French National Cancer Institute (PHRC 2008) and supported by the French National Society of Radiation Oncology (SFRO). Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT2-06-01.