Multi-institutional registry study evaluating the feasibility and toxicity of accelerated partial breast irradiation using noninvasive image-guided breast brachytherapy.

PURPOSE: The noninvasive image-guided breast brachytherapy (NIBB) technique is a novel noninvasive yet targeted method for accelerated partial breast irradiation. We established a multi-institutional registry to evaluate the toxicity and efficacy of this technique across various practice settings. METHODS AND MATERIALS: Institutions using the NIBB technique were invited to participate. Data for acute/late toxicity, cosmetic outcome, and tumor recurrence were collected. Toxicity and cosmetic outcome were graded based on the Common Terminology Criteria for Adverse Events version 3.0 and NRG/Radiation Therapy Oncology Group scale, respectively. Treatment variables were analyzed for association with outcomes. RESULTS: A total of 252 patients from eight institutions were analyzed. The median age was 69 years. The mean tumor size was 1.1 cm (0.1-4.0 cm). Treatment was delivered 10 fractions (34-36 Gy) in 75% and five fractions (28.5 Gy) in 22%. B.i.d. fractionation was used in 9%. Acute radiation dermatitis was Grade 0-1, 2, and 3 in 77%, 19%, and 4%, respectively. One hundred ninety-one patients with a median followup of 18 months (4-72 months) were evaluable for late outcomes. Late toxicity Grades 2 and 3 were observed in 8.8% and 1%, respectively. Cosmetic outcome was excellent, good, and fair/poor in 62%, 36%, and 2%, respectively. B.i.d. fractionation was associated with higher acute and late toxicity. Second-generation applicators were associated with lower late toxicity and better cosmetic outcome. Actuarial freedom from ipsilateral breast tumor recurrence and true recurrence were 98.3% and 98.3% at 2 years and 90.9% and 95.4% at 5 years, respectively. CONCLUSIONS: Accelerated partial breast irradiation using NIBB was well tolerated with a low rate of acute and late toxicity across various practice settings. Ipsilateral breast tumor recurrence and cosmetic outcomes were favorable. b.i.d. fractionation was associated with higher toxicity. Longer followup is needed to confirm late endpoints.

Phase 2 Trial of Accelerated Partial Breast Irradiation (APBI) Using Noninvasive Image Guided Breast Brachytherapy (NIBB).

PURPOSE: Noninvasive image guided breast brachytherapy (NIBB) is a novel approach to delivery of accelerated partial breast irradiation (APBI) that may hold advantages over established techniques. NIBB is not invasive but maintains a high level of precision by using breast immobilization via breast compression and image guidance; it therefore does not require large planning tumor volume margins. We present the primary outcomes of this prospective phase 2 study (BrUOG Br-251). METHODS AND MATERIALS: Eligible patients with early-stage breast cancer underwent NIBB APBI using a dose 34 Gy in 10 fractions delivered daily or twice a day. Treatment was delivered using an Ir-192 high-dose-rate source via specialized applicators. Two orthogonal treatment axes were used for each fraction. The primary endpoints were late toxicity and cosmesis assessed at 2 and 5 years. Toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events v3.0. Cosmesis was assessed using the NRG/Radiation Therapy Oncology Group scale. Ipsilateral breast tumor recurrence was defined as any recurrence or new primary in the treated breast. RESULTS: Forty patients underwent protocol treatment. Median patient age was 68 years (50-92 years). Mean tumor size was 1.1 cm (0.3-3.0 cm). Among the cohort, 62.5% had invasive carcinoma and 37.5% had ductal carcinoma in situ. Thirty-nine percent elected to receive hormone therapy. No grade ≥3 late toxicities were observed at any time point. Grade 2 toxicity was 5% and 10% at 2 and 5 years, respectively. Telangiectasia grade 1 and 2 occurred in 27.5% and 5%, respectively. Breast separation of >7 cm was associated with telangiectasia (P < .01). The rate of good to excellent cosmetic outcome was 95% at 2 years and 100% at 5 years. With a median follow-up of 68 months, the actuarial 5-year freedom from ipsilateral breast tumor recurrence was 93.3% (±4.8%), and overall survival was 93.7% (±4.4%). CONCLUSIONS: NIBB to deliver APBI is well tolerated with a low incidence of significant late toxicity and has favorable cosmetic outcomes. Continued evaluation of the NIBB APBI technique in a larger cohort is warranted.

The rationale, technique, and feasibility of partial breast irradiation using noninvasive image-guided breast brachytherapy.

PURPOSE: Noninvasive image-guided breast brachytherapy (NIBB) is a novel approach to deliver accelerated partial breast irradiation (APBI). NIBB is noninvasive, yet maintains a high degree of precision by using breast immobilization and image guidance. This makes NIBB an attractive alternative to existing APBI techniques. METHODS AND MATERIALS: Forty patients were enrolled to an institutional review board-approved prospective clinical trial evaluating APBI using NIBB. The NIBB technique is described in detail. Briefly, patients were treated with the breast compressed and immobilized sequentially in two orthogonal axes for each fraction. Radiation was delivered using collimated emissions from a high-dose-rate iridium-192 source via specialized applicators. The prescribed dose was 34.0 Gy in 10 fractions. Feasibility and tolerability of treatment were assessed. RESULTS: All patients completed protocol treatment. The median age was 68 years. Sixty-three percent of patients had invasive carcinoma, and 37% had ductal carcinoma in situ. All were node negative. Ninety-three percent of patients were postmenopausal. Mean tumor size, tumor bed volume, and breast volume were 1.1 cm, 22.4 cc, and 1591 cc, respectively. NIBB treatment was well tolerated. Median patient-reported discomfort was 1 on a 10-point pain scale. Treatment delivery times were reasonable. The average treatment time per axis was 14 min (5-20 min), and the average time from start of first treatment axis to completion of orthogonal axis was 43 min (30-63 min). Acute skin toxicity was Grade 0, 1, and 2 in 20%, 53%, and 28% of patients, respectively. There were no Grade 3 or greater acute toxicities observed. CONCLUSIONS: NIBB holds promise as an alternative method to deliver APBI. NIBB is feasible and well tolerated by patients. Further investigation of NIBB to deliver APBI is warranted.