Cancer Patients With COVID-19 Don't Appear To Be At Higher Risk For Blood Clots

Patients with cancer and COVID-19 who are in remission or not on active cancer therapy do not appear to be at increased risk of developing blood clots or venous thromboembolism (VTE), according to preliminary data from the COVID-19 and Cancer Consortium (CCC19).

However, the data should be taken with "a grain of salt," Dr. Rachel Rosovsky, a hematologist/oncologist at Massachusetts General Hospital, in Boston, and member of the medical and scientific advisory board of the National Blood Clot Alliance (NBCA), told Reuters Health by phone.

This is "very early data, not yet mature, with lots of limitations, and we don't want our message to be, don't worry about blood clots in patients with cancer and COVID-19," she said.

Dr. Rosovsky presented this research earlier this month at the International Society on Thrombosis and Haemostasis (ISTH) Virtual Congress, with co-authors Dr. Ang Li, Dr. Jean Connors, Dr. Nicole Kuderer and the CCC19 VTE working group on behalf of the CCC19 consortium.

"VTE is a major cause of morbidity and mortality in patients with cancer. COVID also carries a very high risk as there is coagulopathy associated with COVID," Dr. Rosovsky told Reuters Health.

The findings are based on 2,541 adults (median age, 66 years; 50% women) in the CCC19 registry with laboratory-confirmed SARS-CoV-2 infection or a presumptive diagnosis of COVID-19 and active cancer or a history of cancer.

Only 41% of patients received anti-cancer therapy in the preceding three months. Follow-up was greater than two weeks for 58% of the cohort.

Overall, VTE occurred in 3.7% of patients. The VTE rate by initial COVID-19 severity was 1.2% in mild disease (outpatient), 4.1% in moderate disease (regular hospital ward) and 11.9% in severe disease (intensive-care unit, ICU).

VTE was more common in patients receiving any recent anti-cancer therapy than those without (5.2% vs. 2.5%) and in patients with progressive disease compared to those in remission (6.8% vs. 2.3%).

"Not surprisingly," ICU patients with more severe COVID-19 and those on active therapy or progressive cancer had higher VTE rates than those without those features, Dr. Rosovsky said.

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The highest rates of VTE and pulmonary embolism (PE) were seen in patients with bladder cancer (10.9% and 4.7%, respectively) and those with hematological cancers.

For high-grade non-Hodgkin lymphoma, VTE and PE rates were 7.5% and 3.0%, respectively. For Hodgkin lymphoma, rates were 6.7% and 3.3%, respectively, and for plasma cell neoplasms, 4.4% and 2.2%, respectively.

These early results suggest that patients with cancer and COVID-19 who are not on active therapy appear to experience VTE at a similar rate as other groups. However, given limited follow-up to date, all of these results are "likely an underestimate of true incidence of VTE," Dr. Rosovsky told Reuters Health.

Looking ahead, the researchers are now focusing on patients with 30-day follow-up, on active cancer therapy, as well as hospitalized patients. Their ultimate goal is to inform thrombosis prevention and treatment in patients with cancer and COVID-19.

Unrelated to cancer and COVID-19, Dr. Rosovsky and her colleagues from Venous thromboEmbolism Network U.S. (VENUS), a collaborative U.S. research network, and members from ISTH recently surveyed more than 500 experts in VTE from around the globe who are working on the frontlines of the COVID-19 pandemic.

Dr. Rosovsky told Reuters Health that "the majority of the respondents said all hospitalized patients with COVID should be on prophylactic anticoagulation, but there was significant variation in when to increase the dose, and for how long people needed to be to be on it. There was also wide variation in the numbers of thrombotic complications providers found."

"This speaks to the fact that there still is so much we don't know about VTE risk in COVID-19 and there is an urgent need for collaborative randomized controlled trials to address these critical questions," she said.

—Megan Brooks

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