Adjuvant abemaciclib does not increase delayed reconstructive morbidity after tissue-expander breast reconstruction: A multi-institutional propensity-matched analysis.

BACKGROUND

Abemaciclib, a CDK4/6 inhibitor approved for the adjuvant treatment of HR+/HER2-node-positive early breast cancer, is frequently initiated during the postoperative reconstructive period. However, late postoperative outcomes of adjuvant abemaciclib exposure tissue expander (TE)-based reconstruction are unknown.

METHODS

In this retrospective cohort study, we identified adult women aged 18-75 years with HR+/HER2-breast cancer who underwent TE placement, using the TriNetX platform. The exposed cohort consisted of patients with documented abemaciclib initiation within 180 days of TE placement, and those with no CDK4/6 inhibitor exposure through 12 months postoperatively served as controls. A new-user design excluded patients with any preoperative abemaciclib use. We matched cohorts 1:1 on 35 covariates including disease-severity markers, treatment variables, demographics, and comorbidities. The primary endpoint was a composite major reconstructive complication (MRC)-implant-related infection, implant revision surgery, or mechanical complication-assessed between 6 and 12 months postoperatively. TE removal was evaluated as an independent secondary outcome. Three sensitivity analyses varied the timing of abemaciclib initiation (<6 weeks, 0-90 days, and 91-180 days postoperatively) to test the robustness of the primary findings.

RESULTS

After propensity score matching, 353 matched pairs remained. The MRC composite occurred in 28.9% of abemaciclib-exposed patients versus 27.8% of controls (RR 1.041; 95% CI 0.823-1.316; p = .738). No significant differences were observed for implant-related infection (7.9% vs. 7.1%; RR 1.120), implant revision surgery (22.9% vs. 20.4%; RR 1.125), mechanical complications (13.6% vs. 14.7%; RR 0.923), or TE removal (8.2% vs. 7.9%; RR 1.036). Sensitivity analyses confirmed these null findings across all exposure windows.

CONCLUSION

Postoperative adjuvant abemaciclib was not associated with increased reconstructive morbidity in patients undergoing TE-based breast reconstruction. These findings offer preliminary reassurance that abemaciclib can be integrated into the standard adjuvant treatment timeline without compromising late reconstructive outcomes.