Modifiable Post-Mastectomy Radiation Therapy Factors and Impact on Implant-Based Breast Reconstruction Outcomes.

ABSTRACT

INTRODUCTION: Intensity modulated radiation therapy (IMRT) and other modifiable radiation factors have been associated with decreased radiation toxicity. These factors could allow for improved reconstructive outcomes in patients requiring post-mastectomy radiation therapy (PMRT). However, they have not yet been well-studied in implant-based breast reconstruction (IBBR). METHODS: We performed a retrospective chart review of patients who underwent mastectomy with immediate tissue expander placement followed by PMRT. Radiation characteristics were collected, including radiation technique, bolus regimen, X-ray energy, fractionation, maximum radiation hot spot (DMax), and tissue volume receiving >105% (V105%) or >107% (V107%) of the prescription dose. Reconstructive complications occurring after initiation of PMRT were analyzed with respect to these radiation characteristics. RESULTS: 68 patients (70 breasts) were included in this study. The overall complication rate was 28.6%, with infection being the most common complication (24.3%), requiring removal of the tissue expander or implant in greater than half of infections (15.7%). DMax was greater in patients who required explant after PMRT, and this approached statistical significance (114.5+/-7.2% v. 111.4+/-4.4%, p=0.059). V105% and V107% were also greater in patients who required explant after PMRT (42.1+/-17.1% v. 33.0+/-20.9% and 16.4+/-14.5% v. 11.3+/-14.6%, respectively), however this was not statistically significant (p=0.176 and p=0.313, respectively). There were no significant differences in complication rates between patients with respect to radiation technique or other radiation characteristics studied. CONCLUSIONS: Minimizing the radiation hot spots and volumes of tissue receiving greater than the prescription dose of radiation may improve reconstructive outcomes in patients undergoing IBBR followed by PMRT.