Normal D-dimer levels in cancer patients with radiologic evidence of pulmonary embolism

Accurate and expeditious diagnosis and treatment of pulmonary embolism in cancer patients improves patient outcomes. D-dimer is often used to rule out pulmonary embolism. However, this test is less accurate in cancer patients, and it is unclear whether cancer patients with normal D-dimer levels can present with pulmonary embolism. All consecutive patients who presented to The University of Texas MD Anderson Cancer Center in Houston, Texas, USA, between May 2009 and November 2015 who underwent computed tomography pulmonary angiography and plasma D-dimer level measurement were retrospectively reviewed. Patients with suspected pulmonary embolism and normal D-dimer levels were identified. Among the 8023 cancer patients identified, 1156 (14%) had pulmonary embolism. Only 35 patients with pulmonary embolism (3%) had normal plasma D-dimer levels. Twenty-six of these patients had acute pulmonary embolism and the other nine had subacute or chronic pulmonary embolism. Thirteen of the 26 acute cases were in patients with hematological cancer. Most patients (23/35, 66%) had subsegmental or segmental pulmonary embolism. Only one patient had pulmonary embolism in the main pulmonary arteries. Although it is uncommon (3%), cancer patients with radiologic evidence of pulmonary embolism can present with normal D-dimer levels. Recognizing the possibility of this uncommon occurrence is critical in the decision process for ordering diagnostic tests for evaluation of suspected pulmonary embolism.