Breast Reconstruction Outcomes with Immediate Reconstruction Followed by Proton or Photon Postmastectomy Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> To evaluate breast reconstruction outcomes among women undergoing immediate breast reconstruction (IBR) followed by postmastectomy radiotherapy (PMRT) with photon or proton radiotherapy. <h3>Materials/Methods</h3> We identified consecutive women with breast cancer who underwent IBR followed by unilateral PMRT at our institution from 2015 to 2021 and retrospectively reviewed reconstruction complications. IBR failure was defined as tissue expander or implant removal with loss of reconstruction or conversion to autologous reconstruction. Patient, disease, and treatment characteristics were assessed for association with complications using univariate Cox models. When analyzing the impact of RT-related variables, only complications occurring after the start of RT were included. <h3>Results</h3> Following IRB approval, 225 women were identified as eligible. One-hundred seventy-five (77.8%) elected to undergo prophylactic mastectomy and IBR for symmetry. Two-hundred eighteen patients (96.9%) had two-stage tissue expander-based IBR, and seven (3.1%) had direct-to-implant IBR. One-hundred sixty women (71.1%) were treated with proton therapy. Most (198, 88%) received 50 Gy in 25 fractions, with the remainder receiving 40.05 Gy in 15 fractions (25, 11.1%) or 42.56 Gy in 16 fractions (2, 0.9%). Seven (3.1%) and 28 patients (12.4%) received a boost to the chest wall and lymph node(s), respectively. At a median follow-up of 1.8 years, the 2-year risk of any complication on the irradiated side was 31.4% (24.4-38.3). This is compared to a contralateral risk of 15.0% (9.4-21.7) among the 175 bilateral mastectomy patients. Seventeen patients (7.6%) experienced an ipsilateral IBR failure, six of whom had no final reconstruction. The remaining 11 patients had an autologous reconstruction, two of whom initially planned for autologous reconstruction. There were no contralateral IBR failures. On univariate analysis, increasing age [HR per year: 1.10 (1.05-1.15), <i>p</i><.001], chest wall boost [HR: 4.81 (1.08-21.35), <i>p</i>=.039], and lymph node boost [HR: 3.97 (1.35-11.63), <i>p</i>=.012] were associated with IBR failure. There was no significant difference in IBR failure with protons compared to photons. Administration of capecitabine concurrently with RT predisposed to any complication [HR: 7.97 (1.91-33.33), <i>p</i>=.040], while use of Mepitel film during PMRT was protective [HR for no Mepitel: 1.85 (1.12-3.06), <i>p</i>=.017]. Receipt of neoadjuvant or adjuvant systemic therapy and concurrent T-DM1 were not associated with complications or IBR failure. <h3>Conclusion</h3> Among women who undergo IBR, receipt of PMRT increases the risk of complications by approximately twofold. To our knowledge, this is the largest report on women receiving IBR and proton-based PMRT. There was no difference in IBR failure with protons compared to photons. Despite nearly one-third experiencing complications with IBR and PMRT, most women (92.4%) achieved a successful reconstruction outcome.