Breast boost using noninvasive image-guided breast brachytherapy vs. external beam: a 2:1 matched-pair analysis.

Background: To compare clinical outcomes and toxicity in patients treated with NIBB boost with those in patients treated with external beam (EB) boost.

Patients And Methods: Women with early stage breast cancer treated with WBI and NIBB boost were identified. Control subjects treated with EB boost identified as the best possible match with respect to age, stage, chemotherapy use, and fractionation were chosen for a 2:1 comparison. Acute toxicity, late toxicity, and oncologic outcomes were reviewed. The McNemar nonparametric test was used to evaluate marginal homogeneity between matched pairs.

Results: One hundred forty-one patients were included in the analysis: 47 patients treated with NIBB boost and 94 matched control subjects treated with EB boost (electron, n = 93) or 3-D conformal radiation (n = 1). Grade 2+ desquamation developed in 18 patients (39%) treated with NIBB boost and in 49 patients (52%) treated with EB boost (P = .07). Breast size, electron energy, and fractionation predicted for acute desquamation (P < .0001, P < .001, and P = .006). Median follow-up was 13.6 months. One patient (2%) who received NIBB had Grade 2+ skin/subcutaneous fibrosis 15 months after completion of treatment. Among those treated with EB, 9 patients (9.5%) developed Grade 2+ subcutaneous fibrosis, and 1 patient had recurrent cellulitis. There was statistically significantly less combined skin/subcutaneous toxicity in those treated with NIBB than in those treated with EB (P = .046).

Conclusion: NIBB boost is associated with favorable short-term clinical outcomes compared with EB.