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Purpose/Objective(s) There is a paucity of data regarding the use of whole breast irradiation (WBI) as part of breast conserving therapy (BCT) in women diagnosed with breast cancer who had undergone prior breast implant-based augmentation. In this population, we investigated various factors that impact radiation related toxicities, including the need for additional cosmetic surgery. Materials/Methods A retrospective review was performed for a single institution, with queries done on health-system medical records, radiation therapy medical records, radiology mammography studies, and internal radiation therapy and toxicity databases. We included patients with a prior history of breast implant-based augmentation who subsequently underwent BCT and WBI. Patient and treatment characteristics were collected and reported, and univariate analyses comparing factors correlating with toxicity endpoints were performed. Long-term cosmesis was assessed by the patient's radiation oncologist during routine follow-up visits via the Harvard grading criteria. Results 35 patients treated at our institution between 2006 and 2020 were included in our analyses, with a median follow up time of 2.4 years. Of these, 28 were treated with conventionally fractionated WBI (1.8-2 Gy/Fx) and 7 were treated with hypofractionated WBI (2.66 Gy/Fx). Good/excellent long-term cosmesis was observed in 94% of all patients. 44% of patients ultimately needed additional cosmetic surgery at some point after radiation. Indications for additional surgery included capsular contracture (10), wound complications (2), implant rupture (1), volume loss (1), and asymmetry (1). Fourteen patients (50%) treated with conventionally fractionated WBI and one patient (14%) patient treated with hypofractionated WBI required additional surgery, but this difference was not significant on UVA (P = 0.12). Other factors found not to be significantly associated with rates of additional surgery included BMI, stage, the volume of the breast receiving 105% or 110% of the prescription dose, and presence or absence of bolus during treatment. No patients experienced local or regional recurrence. Conclusion Patients with a prior history of breast implantation often experience good long-term cosmesis with a moderate risk of needing additional future surgery. The use of hypofractionated WBI was not associated with worse cosmetic outcome or an increase in need for additional cosmetic surgery.

To compare outcomes after accelerated partial breast irradiation (APBI) between node-negative and node-positive patients.A total of 534 patients with early-stage breast cancer received APBI including 39 node-positive (N+) cases. Clinical, pathologic, and treatment-related factors were compared between node-negative (N-) and N+ cohorts. Local recurrence (LR), regional recurrence (RR), axillary failure (AF), distant metastases (DM), disease-free survival (DFS), cause-specific survival (CSS), and overall survival (OS) were analyzed.N+ patients were younger (p = 0.04), had larger tumors (p0.001), and were more likely to receive chemotherapy (p0.001). Mean follow-up was 7.8 years for N+ patients and 6.3 years for N- patients (p = 0.06). No differences were seen in 5-year actuarial rates of LR (2.2% vs. 2.6%, p = 0.86), AF (0% vs. 0%, p = 0.69), DFS (90.0% vs. 88.0%, p = 0.79), or OS (91.0 vs. 84.0%, p = 0.65) between the two groups, whereas higher rates of RR (0% vs. 6.1%, p0.001) and DM (2.2% vs. 8.9%, p = 0.005) were noted in N+ patients. A trend for improved CSS (p = 0.06), was seen in N- patients. Age, tumor size, receptor status, T-stage, chemotherapy, APBI technique, and nodal status (p = 0.86) were not associated with LR, while a trend for an association with LR was noted with close/positive margins, (p = 0.07), and failure to receive adjuvant hormonal therapy (p = 0.06).No differences were seen in the rates of LR or AF between N- and N+ patients after APBI. These results support the continued enrollment of node-positive patients in Phase III trials evaluating the efficacy of APBI including the National Surgical Adjuvant Breast and Bowel Project-B39/Radiation Therapy Oncology Group 0413.

Purpose To determine the rates of breast cancer–related lymphedema (BCRL) in patients undergoing whole-breast irradiation as part of breast-conserving therapy (BCT) and to identify clinical, pathologic, and treatment factors associated with its development. Methods and Materials A total of 1,861 patients with breast cancer were treated at William Beaumont Hospital with whole-breast irradiation as part of their BCT from January 1980 to February 2006, with 1,497 patients available for analysis. Determination of BCRL was based on clinical assessment. Differences in clinical, pathologic, and treatment characteristics between patients with BCRL and those without BCRL were evaluated, and the actuarial rates of BCRL by regional irradiation technique were determined. Results The actuarial rate of any BCRL was 7.4% for the entire cohort and 9.9%, 14.7%, and 8.3% for patients receiving a supraclavicular field, posterior axillary boost, and internal mammary irradiation, respectively. BCRL was more likely to develop in patients with advanced nodal status (11.4% vs. 6.3%, p = 0.001), those who had a greater number of lymph nodes removed (14 nodes) (9.5% vs. 6.0%, p = 0.01), those who had extracapsular extension (13.4% vs. 6.9%, p = 0.009), those with Grade II/III disease (10.8% vs. 2.9%, p p = 0.02). Regional irradiation showed small increases in the rates of BCRL ( p = not significant). Conclusions These results suggest that clinically detectable BCRL will develop after traditional BCT in up to 10% of patients. High-risk subgroups include patients with advanced nodal status, those with more nodes removed, and those who receive chemotherapy, with patients receiving regional irradiation showing a trend toward increased rates.

Purpose To examine 10-year results of a single institution's experience with radiotherapy limited to the region of the tumor bed (i.e., accelerated partial breast irradiation, [APBI]) in selected patients treated with breast-conserving therapy (BCT) and compare them with results of matched BCT patients who underwent whole-breast irradiation (WBI). Patients and Methods A total of 199 patients with early-stage breast cancer were treated prospectively with BCT and APBI using interstitial brachytherapy. To compare potential differences in local recurrence rates on the basis of the volume of breast tissue irradiated, patients in the APBI group were matched with 199 patients treated with WBI. Match criteria included tumor size, nodal status, age at diagnosis, margins of excision, estrogen receptor status, and use of adjuvant tamoxifen therapy. Local–regional control, disease-free survival, and overall survival were analyzed between treatment groups. Results Median follow-up for surviving patients was 9.6 years (range, 0.3–13.6 years). Eight ipsilateral breast tumor recurrences (IBTRs) were observed in patients treated with APBI. The cumulative incidence of IBTR at 10 years was 5%. On matched-pair analysis, the rate of IBTR was not statistically significantly different between the patient groups (4%, 95% confidence interval [CI] 1.3–6.7% for WBI therapy patients vs. 5%, 95% CI 1.5–8.5% for APBI patients; p = 0.48). Conclusions Radiation therapy limited to the region of the tumor bed (APBI) produced 10-year local control rates comparable to those from WBI in selected low-risk patients.

Brachytherapy-Based Accelerated Partial Breast Irradiation Versus Canadian Whole Breast Hypofractionation: A Matched-Pair Analysis of Comparative Effectiveness P.Y. Chen, J. Wilkinson, C.S. Shah, J. Wobb, M. Wallace, H. Ye, P. Benitez, N. Dekhne, D. Brabbins, and F. Vicini; Beaumont Health System, Royal Oak, MI, Summa Akron City/St. Thomas Hospitals, Akron, OH, Michigan Healthcare Professionals/21st Century Oncology of Michigan, Farmington Hills, MI

111 Background: We present the results of an analysis of high-risk breast cancer patients as defined by the NSABP B-39/RTOG 0413 phase III trial, all treated with accelerated partial breast irradiation (APBI) from a single institution. Methods: Between July 1993 and August 2010, 130 patients with any combination of at least one of the high-risk features of estrogen receptor (ER) negativity, age < 50, and/or axillary nodal positivity were treated with 1 of 3 forms of APBI. Sixty-seven patients were treated with interstitial needle-catheter brachytherapy, 44 balloon-based brachytherapy and 19 with 3D conformal external beam radiation therapy. Aside from the high-risk features, general eligibility criteria included infiltrating ductal carcinoma, with inclusion of invasive lobular and DCIS since 2003, margins > 2 mm, and surgically staged axilla. One-hundred eighteen patients had one high-risk factor, 11 had two, and 1 had all three factors. The median tumor size was 12.0 mm with margins > 2 mm in 80% of patients. Greater than 75% had T1 tumors and 50% were ER negative. Thirty-one percent of patients were node positive. Based upon the ASTRO Consensus Guidelines for use of APBI (2009) none of these patients were suitable, 38% cautionary and 62% were unsuitable. Results: Median age was 56.5 yrs (range 40-90). With a median follow-up of 5.3 yrs (0.02-16.9) the 5-yr actuarial local recurrence rate (LR) was 4.2%; regional recurrence (RR) was 2.1%. Median time to LR and RR were 1.2 and 2.8 yrs, respectively. On univariate analysis, the only factor significant for LR was a close/positive margin (p=0.031), as ER/PR, age, nodal status, tumor size, histology, grade, hormonal or chemotherapy were all NS. The 5-yr actuarial cause specific, disease-free, and overall survivals as well as distant metastasis were 94%, 91%, 90%, and 6.4%, respectively. Conclusions: This cohort of NSABP B-39/RTOG 0413 identified high-risk patients who have undergone APBI has yielded local-regional control rates and survival outcomes comparable to standard risk patients undergoing partial breast irradiation. Continued follow-up will be needed to assess the long-term efficacy of such high-risk breast cancer patients treated with APBI.