A Study of Dalteparin Prophylaxis in High-Risk Ambulatory Cancer Patients

VTE is an increasingly frequent complication of cancer and anti-cancer therapies. It is associated with increased mortality and other significant adverse consequences. Risk factors for VTE in the cancer population have been identified, and multiple studies have also shown that VTE can be prevented in high-risk populations with the use of thromboprophylaxis. This study evaluated the safety and efficacy of prophylaxis in a high-risk subgroup of cancer patients identified by a validated risk model developed by us previously called the "Khorana Score." Correlative studies evaluated the value of tissue factor as a predictive biomarker of VTE. The purpose of this study was to conduct a prospective, randomized clinical trial comparing the safety and efficacy of prophylaxis with dalteparin to no treatment in reducing VTE in high-risk ambulatory cancer patients initiating chemotherapy and to establish the value of TF as a predictive marker for VTE in ambulatory cancer patients receiving chemotherapy. PHACS was a randomized multi-center clinical trial. Eligible patients were enrolled and underwent baseline screening ultrasonography of the lower extremities to rule out pre-existing DVT and a chest CT scan to rule out PE. If negative, patients were then randomized to receive either dalteparin 5000 units subcutaneously daily or observation for a study period of 12 weeks. The first day of dalteparin prophylaxis coincided with the first day of initiation of a new systemic chemotherapy regimen. The patients were seen every 4 weeks (±1 week) at the time of regularly scheduled chemotherapy cycle visits for serial ultrasonography of lower extremities during study period (i.e. at 4, 8 and 12 weeks.) A chest CT scan was performed at 12 weeks. Compliance was measured by asking patients about missed doses at these 4-weekly visits as well as by asking patients to fill an injection diary.