Primary Prevention of Cancer Associated Thrombosis
Matthew James, MSc Candidate, Translational Medicine and TMED Graduate Student Teaching Assistant
At the September 12 Medical Grand Rounds, the Department of Medicine was fortunate to host Dr. Marc Carrier, a senior clinician-scientist and world-renowned expert in thrombosis from the University of Ottawa. Dr. Carrier’s Grand Rounds presentation focused on the primary prevention of cancer associated venous thromboembolism and highlighted recent evidence from two important clinical trials.
Venous thromboembolism (VTE) refers to blood clots that form in the veins and includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). The incidence of rate of VTE in the general populations is 1 in 1000; however, Dr. Carrier reminded us that the incidence rate is four times greater in cancer patients, and that thromboembolism is the second leading cause of death for cancer patients. Previous evidence for preventative treatment with anticoagulants such as low molecular weight heparins suggested minimal benefit, and many of these treatments resulted in an increased risk of major bleeding.
Direct oral anticoagulants (DOACS) offer a potential for preventative treatment for cancer associated VTE, particularly in high risk patients. Two recent clinical trials (AVERT and CASSINI) examined the role of DOACS in patients who were at high risk for VTE. These trials showed that preventative treatment with DOACS resulted in a significantly lower rate of VTE compared to placebo, with no clinically relevant change in major bleeding events. Since the publication of these trials, the American Society of Clinical Oncology has updated their guidelines to indicate that preventative treatment with DOACS in cancer patients who are at high risk for VTE may be indicated.
Dr. Carrier prefaced his talk by stating that primary prevention for cancer associated VTE is controversial among clinicians. When the audience was polled, there was a fairly even split between those who support the use of DOACS for primary prevention and those who remain unconvinced or do not use DOACS for primary prevention. At our post rounds discussion, Dr. Carrier explained that when new data from clinical trials are published, there is a substantial lag period before this new information is disseminated amongst the medical community. The physicians who are familiar with the latest data from clinical trials are often the ones who form treatment guidelines and are the ones who can most readily implement them in their practice. Thus, in the case of cancer associated VTE, the thrombosis community may be more familiar with the research than physicians in other specialties. Dr. Carrier believes it is the responsibility of those who are familiar with new research to educate those around them. This is not limited to physicians, but should also include nurses, pharmacists and other allied health care professionals who often have more personal contact with patients.
Dr. Carrier also discussed clinical tools such as the Khorana Risk Score which can be used to determine which patients are at higher risk for cancer associated thrombosis. At the Ottawa Hospital, this instrument is integrated into the electronic medical records (EMR), and Dr. Carrier and his colleagues actively use it to assess their patients’ risk for VTE. This assessment tool is not used at every centre, and Dr. Carrier suggested that as more hospitals adopt EMR, integrating these tools may prompt clinicians to familiarize themselves with the research surrounding thrombosis prevention in cancer.
Despite the significant implications for patients, there is limited information in the lay press regarding thrombosis in cancer. This lack of information makes it difficult for patients to educate themselves on the nature of their condition, and thus, they may not know what questions to ask their health care providers regarding their risk for VTE and if preventative treatment is an option. Just as it is important to educate the health care community, Dr. Carrier believes it is extremely important to educate patients about the signs and symptoms of VTE. Patients are often educated about the warning signs of much less common cancer related illnesses, yet often do not know the warning signs of VTE despite. Taking 10 minutes to explain the risks and answer any questions may help reduce avoidable morbidity and mortality.
It was a pleasure to have Dr. Carrier at our first Medical Grand Rounds discussion. On behalf of the TMED graduate students, we thank him for his time and invaluable insight.