Tamoxifen (selective estrogen-receptor modulators) and aromatase inhibitors as potential perioperative thrombotic risk factors in free flap breast reconstruction.

Background: Selective estrogen-receptor modulators and aromatase inhibitors have become ubiquitous in the treatment of breast cancer. However, hormone therapy is a well-established thromboembolic risk factor. The purpose of this study is two-fold: (1) to further evaluate tamoxifen as a potential thrombotic risk factor and (2) to evaluate use of aromatase inhibitors as a potential novel risk factor. Methods: Abdominally based free flaps were reviewed from January of 2008 to July of 2012. Preoperative records were used to identify patients receiving selective estrogen-receptor modulators (e.g., tamoxifen) or aromatase inhibitors before reconstruction. Patients were instructed to cease tamoxifen 2 weeks before surgery. Patients were not advised to cease their aromatase inhibitor regimen. Univariate statistical analyses included Fisher's exact test and the Mann-Whitney U test. A value of p < 0.05 denoted statistical significance. Results: One thousand three hundred forty-seven flaps were performed on 858 patients. There were no statistically significant differences in thrombotic complications or flap failure in comparing those that did not receive preoperative hormone therapy versus those that did receive preoperative hormone therapy, nor were there significant differences specific to those receiving tamoxifen or aromatase inhibitors. A post hoc power analysis was performed with the supposition that hormone therapy exposure results in a two-fold increase in complication rate. The study power was found to be 0.863. Conclusions: Tamoxifen may have been previously overestimated as a microvascular thrombotic risk factor. At a minimum, these data suggest that withholding tamoxifen for 2 weeks before surgery can mitigate thrombotic risk.