Reirradiation with Photon Radiotherapy for Recurrent or New Primary Breast Cancer after Prior Breast Irradiation

Abstract

<h3>Purpose/Objective(s)</h3> Recurrent or new primary breast cancer may benefit from the local and/or regional recurrence risk reduction provided by RT, but delivery of a repeat course of RT is challenging due to risks of potential serious toxicities to organs at risk. This has led to limited use and heterogeneous practice patterns of salvage RT delivery. We hypothesize that breast cancer reirradiation (reRT) may be feasible using modern photon treatment techniques, and we present clinical outcomes and toxicities from a large single institution cohort. <h3>Materials/Methods</h3> In an IRB-approved retrospective study, all consecutive patients with recurrent or new primary non-metastatic breast cancer treated with breast or chest wall (CW) RT and photon reRT from a single institution were identified. Patient and tumor characteristics, treatment parameters, clinical outcomes and toxicities were collected. Recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and overall survival (OS) were defined from reRT start to date of any recurrence, distant recurrence, and death or last follow-up and estimated using Kaplan-Meier methodology. <h3>Results</h3> In total, 126 consecutive patients treated with reRT from 2013-2020 met criteria for analysis. Median age at reRT was 65 years (range 39-88). ReRT was delivered with 3DCRT in 47.6%, VMAT in 46.0%, and static IMRT in 6.4%. Median first, second, and cumulative prescription doses were 60.0 Gy, 46.4 Gy, and 105.0 Gy, respectively. Most received whole breast (WB) (80.2%) or partial breast (PB) (8.7%) initial RT. At reRT, 30.9% were treated to the PB, 11.1% WB/CW, 37.3% WB/CW with comprehensive regional lymph nodes (LN), and 12.8% WB/CW with partial regional LN. Median time between RT courses was 95 months (range 10-361). At a median follow-up of 26.5 months, 9 patients had died. Locoregional, distant, and any recurrence developed in 15 (11.9%), 22 (17.5%), and 28 (22.2%) patients, respectively. Estimated 3-year RFS was 80.7%, DMFS was 80.9%, and OS was 93.2%. Eleven (8.7%) patients developed grade 3 (G3) toxicities (dermatitis (n=8), acute (n=1) and late (n=1) CW pain, decreased joint range of motion (ROM) (n=1)); no G4 or G5 toxicities occurred. Five (4.0%) patients developed rib fracture. Of 23 patients retreated to a reconstructed CW, 30.4% and 34.8% developed Baker G1-2 or G3-4 implant contracture, respectively. Four patients had significant brachial plexus overlap, of whom 1 developed G2 decreased joint ROM and G2 soft tissue fibrosis and 1 developed G3 decreased joint ROM. <h3>Conclusion</h3> In the largest institutional experience to date on the use of photon reRT for recurrent or new primary breast cancer, reRT is associated with low rates of severe adverse events. In this high-risk population, locoregional and distant disease control rates are high. Further prospective study is needed to define the optimal treatment volume, prescription dose selection, and cumulative dose constraints with reRT to maximize the likelihood for successful and safe salvage therapy.