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

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).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.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.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.