Abstract P4-11-13: A Multi-Institutional Assessment of the Feasibility, Implementation, and Early Clinical Results with Noninvasive Image-Guided Breast Brachytherapy for Tumor Bed Boost

Abstract

Abstract Background: Noninvasive image-guided breast brachytherapy (NIIGBB) is an FDA-approved, commercially available (AccuBoost®, Billerica, MA) mammography-based, breast brachytherapy system whereby the treatment applicators are centered on the planning target volume (PTV) to direct 192Ir emissions along orthogonal axes. This study evaluates the feasibility, implementation, and early results of NIIGBB for breast tumor bed boost in combination with external beam whole breast radiation therapy (WBRT), as part of post-lumpectomy radiation. Material and Methods: A privacy-encrypted online data registry was created to collect clinical and technical information from 8 independent academic and community-based institutions. Data were collected from consecutive 110 individual women with early stage breast cancer after breast conserving surgery, who received adjuvant WBRT (mean dose 48.3 ± 2.5 Gy) and tumor bed boost with NIIGBB between July, 2007 and March, 2010. Of the patients, 74% had invasive cancer, with 80% ER+ and 34% HER2+. NIIGBB was delivered before, during, or after WBRT in 57%, 39%, or 4% of the patients. Patient age and lumpectomy cavity size ranged from 32-88 yrs and 0.1-5.3 cm, respectively. Boost dose was delivered in 1.9 ± 0.3 Gy/fx for a total of 12.9 ± 3.4Gy. Toxicity and cosmesis were evaluated after radiation therapy and graded according to the Common Toxicity Criteria (v3.0) and the Harvard scale. Median follow up was 6 months (1-17 months). Results: Grade 1-2 skin toxicity was observed in 18%, 7%, and 0% during the acute (1-3wks), intermediate (4-26 wks), and late-intermediate (>26wks) periods. There were no Grade 3 or higher skin toxicity events. At 6 months, for the entire cohort, cosmetic grading was excellent, good, fair/poor in 52%, 48%, and 0%. The breast compression achieved for each treatment session was remarkably consistent with a mean mammographic plate separation of 6.4 ± 0.3 cm. Breast compression was scored as “uncomfortable” when NIIGBB was delivered before or during WBRT. The mean total duration of set-up and treatment per fraction was 16.7 ± 2.1 min. For each patient, the fraction-to-fraction variability in estimated PTV was low as 69% of treatments were completed with the same applicator size. Discussion: These data indicate that NIIGBB is feasible and can be consistently implemented in a broad array of practice settings. Preliminary evaluation suggests that NIIGBB is associated with acceptably mild normal tissue toxicity and favorable early cosmetic results. The application of NIIGBB before completion of WBRT may be associated with better patient tolerance at the expense of slightly less favorable short-term cosmetic outcome. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-11-13.