Reply: Perioperative Tamoxifen Use and Risk of Deep Vein Thrombosis

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Sir:
We thank the authors for reading our study and appreciate their interest in our work. We agree that multiple factors must be considered when evaluating the risk of microvascular flap thrombosis. Risk assessment for venous thromboembolism (VTE) is also critical in all hospitalized patients, and therefore in any patient undergoing breast reconstruction with autologous tissue transfer. Indeed, the Caprini Risk Assessment Model (RAM)1 is an important tool in determining this risk that has been validated in the plastic surgery patient population.2 However, the purpose of our study was to assess the role of tamoxifen in microvascular flap thrombosis, and not deep venous thrombosis, because several high-level studies have already confirmed the increased risk of VTE in patients taking tamoxifen.2–5
In our patient population, there were no significant differences in the rates of VTE between the tamoxifen and control groups. The Caprini RAM, however, does not take tamoxifen use into consideration. Additionally, this model does not always accurately predict VTE risk in certain plastic surgery populations as seen in studies on spinal cord injury patients after reconstructive surgery.6,7 Irrespective of this, we urge caution in strictly translating the practices surrounding the prevention and treatment of VTE to the prevention and treatment of clot formation at the microanastomosis.
Although the increased risk of VTE secondary to tamoxifen use8 initially led to the concern for an increased risk of microvascular flap thrombosis in patients taking tamoxifen, these two phenomena are not necessarily identical. As discussed in our article, there are likely several differences in the pathophysiology of clot formation between large lower extremity veins and microvasculature in flap pedicles. Such factors may include the timing of endothelial injury, exposure to systemic factors, stasis of blood and trauma caused by microanastomosis, among others. Additionally, as the authors describe, the etiology of microvascular flap thrombosis is multifactorial, and includes radiation, patient demographics, flap choice and reconstruction timing, among others, which must be considered in conjunction with tamoxifen therapy.
We agree that the Caprini RAM is an important tool in assessing the risk of VTE and should be used appropriately. Similarly, we do not dispute the well-documented evidence of the increased risk of VTE in patients taking tamoxifen. However, we believe that this risk may not imply the need to hold tamoxifen before microvascular procedures, given the current evidence, and hope that continued research in this area will better define the role of tamoxifen, if any, in influencing the outcomes of microvascular breast reconstruction.

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