Incidence of Thromboembolic Events in Cancer Hospitalized Patients With COVID-19.

To the Editor:

In a recent article published in CHEST (March 2021), Jiménez et al conducted a systematic review about the current evidence on the incidence of venous thromboembolic events (VTE) among hospitalized patients with COVID-19. In this article, 48 observational studies were reviewed, detecting an overall incidence of VTE of 17.0%. This incidence was higher in prospective studies including thrombosis screening (33.1% vs 9.8% in clinical diagnosis) and patients admitted to the ICU compared with those admitted to the ward (27.9% vs 7.1%, respectively). In this review, 24% of the total population included in all studies were cancer patients. However, throughout the article there is no reference to this patient subgroup being the most affected by COVID-19. Further sub-analysis was made that allows us to understand what consequences could have a more prothrombotic state in patients with an already greater risk of developing VTE.

Cancer patients have inherently 4 to 7 times the risk of developing VTE. As described by Bakouny et al, there is no clear evidence of increased thrombosis in cancer and COVID-19. However, even though there are no studies to support it, they conclude that VTE diagnoses in these patients are probably being underestimated because of strong evidence of a cancer procoagulant state. Nevertheless, in the only study published with cancer patients diagnosed with COVID-19, the incidence of thrombosis was not increased in oncological patients. Patell et al detected a cumulative incidence of VTE of 18.2% in the non-cancer cohort and 14.2% in the cancer cohort. Survival was significantly shorter in the group with active cancer (P = .038), but, surprisingly, the cumulative incidence of major and fatal bleeding was similar, 20.8% in the non-cancer group and 19.5% in the cancer cohort.

Therefore, a great question must be answered: Is there really a procoagulant summation effect between cancer and COVID-19? We hypothesized that when cancer patients develop the COVID-19 cytokine storm that could generate VTE, these patients are already in a critical situation with a high mortality (in our series approximately 40%), probably dying without time enough to develop thrombosis, or they may be underdiagnosed in those critically ill patients with a very bad prognosis, especially in the first weeks of the pandemic. These points might be the reasons for a lower cumulative incidence of VTE in cancer patients.