Is boost therapy necessary in the treatment of DCIS?

Abstract

537 Background: Whole breast irradiation therapy following lumpectomy for invasive breast cancer (IBC) and non-invasive breast cancer (DCIS) significantly reduces the risk of local recurrence. Boost radiation therapy to the tumor bed has been proven to additionally lower the risk of recurrence for IBC. The benefit of boost therapy in patients with DCIS is less certain. We carried out a review of NSABP B-24 to assess the benefit of boost therapy in this randomized trial. Methods: 1,804 women with DCIS were randomized in NSABP B-24 following lumpectomy and radiation therapy to placebo (902) or tamoxifen (902). Whole breast irradiation therapy (50 Gy) was mandatory. Boost radiation therapy was optional. 1,569 patients (86.97%) were identified as having complete data for analysis. 692 of these patients received boost therapy ranging from 1 Gy -20 Gy with 81.5% receiving 10 Gy. Median follow-up time was 14.2 years for the boost group and 14.3 years for the non-boost group. Results: Patients receiving a boost had a significantly higher rate of involved margins (21.0% vs. 14.7%, p=0.002) and comedo necrosis (52.1% vs.45.3%, p=0.008). Margin status (HR: 2.31, p=0.0026), comedo necrosis (HR: 1.5, p=0.031), and age (HR: 0.96, p<0.001) were significant predictors of ipsilateral breast tumor recurrence (IBTR). Boost had no significant impact on IBTR (HR:1.12, p=0.69). There was no significant interaction between boost and treatment (HR: l.04, p=0.91), boost and margin status (HR: 0.77, p=0.52), and boost and comedo necrosis (HR: 0.74, p=0.31). The lack of boost interaction was true for both invasive and non-invasive IBTR. Conclusions: In this unplanned analysis of NSABP B-24 the addition of boost radiation therapy was not found to be of value in reducing the recurrence of invasive or noninvasive breast cancers for patients with DCIS. No significant financial relationships to disclose.