P3-13-01: Boost Radiation Therapy Not of Value in Reducing IBTR of Invasive or Noninvasive Breast Cancers for Patients with DCIS: Results from the NSABP B-24 Trial.

Abstract

Abstract Background: Whole breast irradiation therapy following lumpectomy for invasive breast cancer (IBC) or noninvasive 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 the NSABP B-24 trial to assess the benefit of boost therapy. Methods: After lumpectomy and radiation therapy, 1804 women with DCIS were randomly assigned to placebo (902) or tamoxifen (902). Whole breast irradiation therapy (50 Gy) was mandatory. Boost radiation therapy was optional, and boost status was known for 1,569 patients. Of these, 1392 patients (86.97%) were identified as having all data sufficient for multivariate analysis. Of these, 613 received boost therapy ranging from 1 Gy −20 Gy, with 81.5% receiving 10 Gy. Mean time of follow-up was 161 months. Results: Patients who received boost radiation therapy were more likely to be younger (p=0.04), have positive margins (p=0.007), and be more likely to have comedo necrosis (p=0.03). Multivariate analysis identified only treatment (tamoxifen vs placebo) (HR=0.74, 95% CI=0.57−0.98, p=0.034), age (≥ 50 verses < 50) (HR=0.47, 95% CI=0.36−0.61, p<0.0001), and margin status (positive vs negative) (HR: 1.79, 95% CI= 1.31−2.43, p<0.001) as significant predictors for ipsilateral breast tumor recurrence (IBTR). Boost had no significant effect on IBTR (HR=0.87, 95% CI=0.66−1.15, p=0.33). The lack of boost effect applied to both invasive (HR=0.86, 95% CI=0.58−1.27, p=0.44) and noninvasive IBTR (HR=0.89, 95% CI=0.60−1.33, p=0.56). No interaction was seen between boost and treatment, age, margin status, or comedo necrosis. Conclusion: In NSABP B-24, the addition of boost radiation therapy was not found to be of value in reducing IBTR of invasive or noninvasive breast cancers for patients with DCIS. Supported by PHS grants NCI-U10-CA-69651, NCI-U10-CA-12027, and NCI P30-CA-14599 from the US NCI and AstraZeneca. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-13-01.