Venous thromboembolism in cancer patients receiving neoadjuvant chemotherapy: a systematic review and meta-analysis

Background: Venous thromboembolism (VTE) is a frequent complication in cancer patients receiving adjuvant treatment. The risk of VTE during neoadjuvant chemo-radiotherapy remains unclear. Objectives: This systematic review evaluated the incidence of VTE in patients with cancer receiving neoadjuvant treatment. Methods: MEDLINE and EMBASE databases were searched from inception to October 2017. Search results were supplemented with screening of conference proceedings of the American Society of Clinical Oncology (2009-2016) and the International Society of Thrombosis and Haemostasis (2003-2016). Two review authors independently screened titles and abstracts, and extracted data onto standardized forms. Results: Twenty-eight cohort studies (7827 cancer patients, range 11 to 1398) were included. Twenty-five had a retrospective design. Eighteen cohorts included patients with gastrointestinal cancer, representing over two-thirds of the whole study population (n = 6002, 78%). In total, 508 of 7768 patients were diagnosed with at least one VTE during neoadjuvant treatment, for a pooled VTE incidence of 7% (95% CI, 5% to 10%) in the absence of substantial between-study heterogeneity. Heterogeneity was not explained by site of cancer or study design characteristics. VTE presented as pulmonary embolism in 22% to 96% of cases (16 cohorts), and it was symptomatic in 22% to 100% of patients (11 cohorts). The highest VTE rates were observed in patients with bladder (10.6%) or esophageal (8.4%) cancer. Conclusions: This review found a relatively high incidence of VTE in cancer patients receiving neoadjuvant therapy in the presence of some between-study variation, which deserves further evaluation in prospective studies.