PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): The NIBB technique is a novel non-invasive but targeted method of delivering partial breast irradiation. We established a multi-institutional registry to evaluate feasibility, safety, and efficacy of this technique across various practice settings.
Materials/Methods: All centers employing the NIBB technique were invited to participate. Patients treated with NIBB APBI were registered on a privacy-encrypted online data registry. Patient demographics, tumor characteristics, and treatment parameters were recorded. Outcomes data for acute toxicity, late toxicity, cosmetic outcome, and ipsilateral breast tumor control were collected. Toxicity and cosmetic outcome were graded based on the Common Terminology Criteria for Adverse Events v3.0 and Harvard Scale, respectively.
Results: 154 patients with a mean age of 68 years (range: 50-92 years) underwent APBI using NIBB. The mean tumor size was 1.1 cm (range: 0.1 – 3 cm). Histology was IDC in 64%, DCIS in 21%, and ILC in 3%. 92% were ER positive and 3% were HER2-neu positive. All patients were lymph node negative. Margins were <0.1 mm, 0.1-1.9 mm, and ≥ 2 mm, in 9%, 21%, and 64%, respectively. Treatment doses were 34Gy in 10fx, 36Gy in 10fx, and 28.5Gy in 5fx in 55%, 11%, and 27% of patients, respectively. 12% were treated BID. Mean breast separation with compression was 6.4 cm (3.0 – 9.4 cm). Acute radiation dermatitis was grade 0-1 in 124 patients (81%), grade 2 in 28 patients (18%), and grade 3 in 2 patients (1%). 124 patients were evaluable for late toxicity and cosmetic outcome. Grade 3 late toxicity was observed in 1 patient (<1%) with fat necrosis. Grade 2 toxicity was seen in 6% of patients with 1 hyperpigmentation, 5 telangiectasia, 2 fibrosis, and 1 breast pain. Cosmetic outcome at last follow up was Excellent, Good, and Fair/Poor in 69%, 31%, and 1%. At a median follow up of 18 months (1 - 72 months), ipsilateral breast tumor control was 98%.
Conclusion: APBI delivered using NIBB is well tolerated with a low rate of significant acute toxicity. Late toxicity and cosmetic outcome are also favorable. Longer follow up is needed to confirm late end points.
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