Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_8_3396 - Re-irradiation of Local-regional Disease in Breast Cancer Using Modern Radiation Techniques: Preliminary Results of Tolerability and Efficacy

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Re-irradiation of Local-regional Disease in Breast Cancer Using Modern Radiation Techniques: Preliminary Results of Tolerability and Efficacy
J. G. Bazan, J. L. Wobb, D. J. DiCostanzo, E. Healy, and J. R. White; The Ohio State University Wexner Medical Center, Department of Radiation Oncology, Columbus, OH

Purpose/Objective(s): Local-regional recurrences (LRR) of breast cancer after primary treatment with lumpectomy+radiation therapy (RT) or mastectomy+/-RT are uncommon. Isolated LRR is curable but even when distant disease is present, symptomatic LRR may require durable palliation. These cases represent therapeutic dilemmas in the setting of prior (pRT). The indications for re-irradiation (re-RT), the optimal dose and technique are unknown. We use inverse planned intensity-modulated radiation therapy (IMRT)/volumetric modulated arc radiotherapy (VMAT) to optimally cover the targets and spare normal tissues in the re-RT setting. We hypothesize that re-RT with IMRT/VMAT results in acceptably low grade ≥3 acute toxicity (<10%) with acceptable in-field control.

Materials/Methods: We queried our department’s radiation database for breast cancer patients treated with IMRT/VMAT from 2014-2017. We reviewed the electronic record for each case to determine receipt of pRT. For each case of re-RT, demographic, disease characteristics, pRT/re-RT details, toxicity and outcome were collected. Local relapse (LR) was classified as progresion documented within the irradiated field. All other relapses were classified as distant (DR). Freedom from LR (FFLR) and DR (FFDR) were calculated from the end of re-RT using the Kaplan-Meier method.

Results: Of 269 patients treated with IMRT/VMAT, 28 patients received re-RT (18 isolated LRR, 10 LRR with simultaneous distant disease). The median pRT total dose to the breast/chestwall was 50.4 Gy (IQR, 50.4-61.8 Gy). The majority (53.6%) received pRT to the supraclavicular fossa/axillary apex and a minority (10.7%) received pRT to the internal mammary nodes. The median time from pRT to re-RT was 60 months (IQR, 36-105 months). 11 patients received concurrent chemotherapy. Curative intent re-RT was given to 22/28 patients, including 3 patients with high cervical nodes and 1 patient with mediastinal disease. The most common re-RT dose/fractionation was 45 Gy/1.5 Gy fractions BID (N=12). Median re-RT dose was 45 Gy (IQR, 42.3-50 Gy) in 2 Gy/fx (IQR, 1.5-2.3 Gy); 50% of patients received a boost to a median total re-RT dose of 60 Gy (IQR, 54-64 Gy). There was 1 case of acute grade 3 toxicity (3.6%): esophagitis in a patient that received 45 Gy/1.5 Gy BID with a 15 Gy/1.5 Gy BID boost that included mediastinal disease. There was 1 case of grade 3 wound dehiscence that developed 3 months after re-RT. There were no cases of brachial plexopathy. Median follow-up was 1 year (IQR, 5-25 months) with 1-year FFLR=91.7% and FFDR=47.4%.

Conclusion: Re-RT for LRR breast cancer with IMRT/VMAT is well tolerated with a low rate of severe acute toxicity. Mature follow-up is needed to adequately characterize the late toxicity. Local control with this approach is excellent but these patients remain at high risk of DR. Even at a single institution, we identified variations in dose/fractionation underscoring the importance of well-designed, prospective trials to identify the optimal re-RT approach.

Author Disclosure: J.G. Bazan: None. J.L. Wobb: None. D.J. DiCostanzo: None. E. Healy: None. J.R. White: Co-chair, Breast Cancer Committee; NRG. Member; NCI Breast Cancer Steering Group.

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