Unsuspected pulmonary embolism in cancer patients: a narrative review with pooled data

Detection of pulmonary embolism (PE) is not uncommon in patients undergoing computed tomography (CT) for routine staging of malignancy. Several studies have been conducted in recent years to evaluate the impact of unsuspected pulmonary embolism (UPE) on the prognosis and management of cancer patients. We aimed at summarizing the available evidence, to improve the understanding of the frequency and clinical significance of UPE in terms of survival, recurrent venous thromboembolism (VTE) and major bleeding. Medline was searched up to the end of September 2013, by using the terms "unsuspected pulmonary embolism" OR "incidental pulmonary embolism" OR "asymptomatic pulmonary embolism". We found 552 out of 35,990 cancer patients diagnosed with UPE (14 studies), for a mean weighted prevalence of 1.82 % (95 % CI 1.47-2.21). When comparing cancer patients diagnosed with UPE to those presenting with symptomatic PE, we found a pooled OR of 0.96 (95 % CI 0.58-1.57) for mortality (3 studies), 0.87 (95 % CI 0.47-1.60) for recurrent VTE (4 studies) and 0.90 (95 % CI 0.43-1.88) for major bleeding (4 studies). In conclusion, UPE represents a non-infrequent finding on CT scans ordered for reasons other than suspected PE and is a challenging clinical situation in the management of cancer patients. Even if UPE is generally milder in the short term, it may share a similar impact on survival and recurrent VTE, as compared to symptomatic PE. Large collaborative projects and, hopefully, interventional trials are needed to clarify the best management strategies.