An incidental clot: a decision the evidence cannot make

Review and sources

Not clinically reviewed. No clinician has signed this scenario.

• Lyman GH, Carrier M, Ay C, et al. American Society of Hematology 2021 guidelines for management of venous thromboembolism: prevention and treatment in patients with cancer. Blood Adv. 2021;5(4):927-974. Recommendation 26: for patients with cancer and incidental (unsuspected) pulmonary embolism, the panel suggests short-term anticoagulation treatment rather than observation (conditional recommendation, very low certainty in the evidence of effects). No systematic review or randomised trial addressed the question; certainty judged very low for risk of bias, inconsistency and imprecision; named a research priority. Mortality RR 0.81 (95% CI 0.67-0.98), 89 fewer per 1000; symptomatic PE RR 0.36 (0.18-0.72), 77 fewer per 1000; major bleeding RR 3.00 (1.21-7.47), 128 more per 1000. Good practice statement 1: consideration of treatment should rest on the individual risk of thrombosis and major bleeding after full discussion of the potential benefits and harms.
• van der Hulle T, den Exter PL, Planquette B, et al. Risk of recurrent venous thromboembolism and major hemorrhage in cancer-associated incidental pulmonary embolism among treated and untreated patients: a pooled analysis of 926 patients. J Thromb Haemost. 2016;14(1):105-113. Incidental pulmonary embolism is defined as pulmonary embolism diagnosed on computed tomography not performed for suspected pulmonary embolism, estimated to occur in 3.1% of all cancer patients. Weighted pooled six-month risks across 11 cohorts: recurrent VTE 5.8%, major haemorrhage 4.7%, mortality 37%. Recurrence 12% in untreated patients. Recurrence risk after subsegmental incidental embolism comparable to more proximal (HR 1.1, 95% CI 0.50-2.4).
• Peris M, Jiménez D, Maestre A, et al. Outcome during and after anticoagulant therapy in cancer patients with incidentally found pulmonary embolism. Eur Respir J. 2016;48(5):1360-1368. In 715 RIETE registry patients, during anticoagulation the rate of major bleeding exceeded the rate of symptomatic pulmonary embolism (10.1 versus 3.17 per 100 patient-years) and fatal bleeding exceeded fatal pulmonary embolism; the authors conclude the risk-benefit ratio of anticoagulant therapy in these patients is uncertain and must be evaluated in further studies.