Background <p>Breast reconstruction surgery (BRS) has increased in prevalence over recent decades. However, little is known about whether undergoing BRS influences the choice of radiotherapy modality after surgery. This study compares associations between BRS and types of postmastectomy radiation treatment modalities for breast cancer.</p> Methods <p>Using the National Cancer Database (NCDB) Breast Participant Use File (PUF) from 2004 to 2018, we evaluated usage of four different postmastectomy radiation treatment modalities – 2D therapy, 3D conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), and external beam radiation (EBR)—among patients who received BRS versus those who did not.</p> Results <p>Our study suggests that BRS patients had higher odds of receiving advanced radiotherapy. For Phase I, BRS patients were 3.27 (95% CI 2.70–3.96) times more likely to receive 3D-CRT vs. 2D-therapy, and 3.42 (95% CI 2.82–4.15) times more likely to receive IMRT vs. 2D-therapy, with relatively equal rates of receiving IMRT compared to 3D-CRT (1.05; 95% CI 0.97–1.12). For Phase II, BRS patients were 1.59 (95% CI 1.49–1.70) times more likely to receive 3D-CRT vs. 2D therapy, 1.53 (95% CI 1.39–1.69) times more likely to receive IMRT vs. 2D therapy, and 1.16 (95% CI 1.11–1.21) times more likely to receive unspecified EBR vs. 2D therapy.</p> Conclusions <p>Overall, patients undergoing BRS are significantly more likely to receive IMRT and 3D-CRT compared to those who did not undergo reconstruction. This pattern is likely driven by the anatomical considerations of BRS but may also reflect disparities in access to care. Understanding these differences is crucial for promoting equitable, high-quality oncologic care and optimizing long-term outcomes for patients undergoing breast reconstruction surgery and radiation therapy.</p> <p>Level of evidence: Level III, risk/prognostic study.</p>