D122. The Impact of Tamoxifen Therapy on Thrombotic Flap Complications: A Nationwide Analysis

PURPOSE: Perioperative tamoxifen practices in microvascular breast reconstruction vary widely. However, no prior literature has investigated this issue from a national standpoint. Thus, this study investigated: (1) the impact of tamoxifen therapy on microvascular flap outcomes using nationwide data, and (2) amongst those on tamoxifen therapy, the impact of perioperative tamoxifen use on flap outcomes. METHODS: This was a retrospective cohort investigation using Truven MarketScan Databases (2014-2017). All women who underwent microvascular breast reconstruction were included; prescriptions claims data was used to identify those on tamoxifen. Outcomes were compared between tamoxifen/non-tamoxifen cohorts. Subgroup analyses in the tamoxifen cohort were undertaken to investigate whether perioperative tamoxifen use impacted outcomes. RESULTS: Overall, 5,832 women were included, of whom 1,983 (34%) were on tamoxifen. There were no differences in flap-related adverse events between tamoxifen and non-tamoxifen cohorts (OR: 1.00; 95%CI: 0.79-1.31; p=0.38). However, amongst patients determined to be at high risk for thrombotic complications, those on tamoxifen therapy had a significantly higher risk of 90-day postoperative venous thromboembolism (OR: 1.15; 95%CI: 1.01-1.28; p=0.04). There were no significant differences in flap failure between those who held tamoxifen versus those who continued tamoxifen into the perioperative period. CONCLUSION: Upon review of national data, preoperative tamoxifen therapy did not significantly increase flap complications/failure after microvascular breast reconstruction. However, patients on tamoxifen therapy with thrombotic risk factors as determined by the Caprini risk score were found to have greater risk for postoperative venous thromboembolism- such patients may need special consideration for postoperative chemoprophylaxis.