Effect of Prepectoral Versus Subpectoral Implant-Based Reconstruction on Post-Mastectomy Radiation Dosimetry.

Background: The placement of breast implants in a prepectoral plane has become increasingly popular in breast reconstruction, although data on how this affects radiation delivery in women with breast cancer are limited. This study aimed to assess the dosimetric differences in radiation plans for immediate breast reconstruction between prepectoral and subpectoral implants.

Methods: In this study, a retrospective review and dosimetric analysis of patients with breast cancer who underwent immediate implant-based reconstruction and postmastectomy radiation therapy (PMRT) were performed. Patients with pre- or subpectoral implants were matched 1:1 by use of boost and radiation field. Demographics and complications were compared using the Mann-Whitney U test for continuous variables and the chi-square test for categorical variables. Dosimetric data were analyzed to compare doses to the target, heart, lungs, and pectoralis major using a Mann-Whitney U test.

Results: The study identified 42 patients who met the inclusion criteria. Planning target volume (PTV) coverage was better in the prepectoral group (PTV D95%, 45.61 vs. 43.38 Gy; p = 0.04). The heart and lung doses did not differ. The patients with subpectoral implants had a lower absolute volume of pectoralis major receiving 20 to 45 Gy.

Conclusion: This assessment of radiation dosimetry for patients undergoing immediate breast reconstruction found that the primary dosimetric difference between prepectoral and subpectoral implants was the dose to the pectoralis major. Otherwise, no significant difference in target coverage was found. These data suggest that implant placement can be selected to optimize reconstructive outcomes, with less concern for compromise to the oncologic quality of PMRT.