Outcomes For Apbi With Strut-Based Brachytherapy: First 200 Accrued Patients (52-Month Median Follow-Up)

The SAVI Collaborative Research Group (SCRG) was created to study the long-term outcomes of women receiving accelerated partial breast irradiation (APBI) using strut-based applicators. The outcomes for the first 200 accrued patients in the study (n = 200) are reported for all subjects, as well as stratified by DCIS or invasive histology. Patients for this subset analysis were taken as the initial 100 treated across all participating sites. Median follow-up of this cohort was 52.3 months at the time of the abstract. Patients were treated with APBI using the strut-based brachytherapy device with conventional dose and fractionation (3.4 Gy x 10 fx, BID). Treatment planning goals for the planning target volume were a V90 > 90%, V150 < 50 cc, and V200 < 20 cc. Patients were followed regularly by their radiation oncologists and outcome was graded based on the CTCAE v3.0 (common terminology criteria for adverse events, version 3.0). Recurrence (raw and actuarial) rates were also calculated based on the follow-up. Cosmesis was graded using the Harvard Scale. 149 patients had invasive disease and 51 had ductal carcinoma in situ. The median age was 62.0 yrs (range 40-85 yrs), with 84% post-menopausal. Median tumor size was 10.5 mm (range 0.0-55 mm) with 88% being estrogen receptor positive. All patients completed APBI as planned with no serious adverse events. All patients met the dosimetric criteria. Late toxicity (grade ≥ 2) rates were low; telangiectasias (1.6%), seroma (3.2%) and fat necrosis (0.5%). Good/excellent cosmesis was seen in > 93% of subjects at all times of follow-up (6 months to 60 months). Local control was excellent with a true recurrence/marginal miss rates of 1.5% (n = 3), 1.4% (n = 2) and 2.0% (n = 1) for all subjects, invasive and DCIS subgroups, respectively. The ipsilateral/elsewhere recurrence rate was 1.0% (n = 1), 1.4% (n = 2) and 0% (n = 0) for all subjects, invasive and DCIS subgroups, respectively. The 4-yr actuarial rates for TR/MM were 1.8%, 1.7%, and 2.1% for all subjects, invasive and DCIS subgroups, respectively. For these initially treated 200 patients with a median 52 months of follow-up, strut-based brachytherapy appears to be a well-tolerated, effective treatment with low rates of toxicities. Local control rates are as good as those for other brachytherapy-based APBI techniques. With APBI an acceptable treatment for many women with early-stage breast cancer, strut-based brachytherapy continues to be versatile, safe, and effective.