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Is Venous Thromboembolism in Asian Patients Undergoing Gastrectomy Different From Venous Thromboembolism in Their Western Counterparts?

In this issue of JAMA Surgery, Jung and colleagues1 examine the safety and efficacy of venous thromboembolism (VTE) prophylaxis in Korean patients undergoing gastrectomy for cancer. Their randomized clinical trial found decreased postoperative VTE with the use of low-molecular-weight heparin in addition to mechanical prophylaxis, compared with the use of mechanical prophylaxis alone. However, the authors claim that, because the VTE rate was low and the rate of bleeding was increased, VTE prophylaxis (low-molecularweight heparin plus intermittent pneumatic compression) still may not be the right choice for all patients undergoing gastrectomy. Although we were pleased to see this focus on VTE, which until recently was understudied in Asian patients,2 we do have some questions about this trial and its conclusions. First, why were VTE rates so low among patients in this study? Is it because of genetics? The relatively low incidence of VTE in Korean patients compared with patients from other ethnic backgrounds has been attributed to genetics.3 The existing VTE prophylaxis guidelines for patients with cancer are based on Western data, and no agreement has been reached about prophylaxis for Asian patients with gastric cancer.4 Is the rate low because of the surgical approach? Laparoscopic gastrectomy has gained popularity with outcome benefits, including shortened length of hospital stay; earlier functional recovery; and lower mortality and morbidity, including rates of VTE. Do the differing ratios of open to laparoscopic surgery in the 2 arms influence the results? Second, we were impressed that the study was a randomized clinical trial in which all patients followed a specified perioperative clinical pathway. However, there was no concealment of VTE prophylaxis allocation. Why did the authors not blind the clinicians to the assigned arm? Blinding can reduce the threat to validity from surveillance bias, in which some outcomes are tested for and identified more frequently or are treated differently when the clinicians know to which treatment arm the patients have been assigned. Surveillance bias has been known to influence VTE rates in surgical populations.5,6 Bleeding could also have been diagnosed or managed differently (ie, return to surgery and/ or transfusion), according to whether or not the patient was given pharmacological VTE prophylaxis. Third, what about VTE occurrence later in the hospital course or after discharge? All patients in the trial underwent duplex ultrasonography on postoperative day 4. The accepted terminology has changed from hospital-acquired to hospital-associated VTE because many VTE events occur after discharge rather than immediately after surgery.7 The American College of Surgeons National Surgical Quality Improvement Program measures 30-day postoperative complications. Why did the authors not do the same? Did any patients have later VTE occurrence? Overall, we commend the authors for producing a clinical trial on an important topic in cancer surgery. They shed light on VTE prevention through the lens of precision or personalized medicine and offer compelling data on the need for future research to define optimal VTE prevention in selected populations.