To investigate the association of androgen deprivation therapy (ADT) for prostate cancer with thromboembolic events.

PubMed, Web of Science, and Scopus were queried on April 5, 2017 for systematic review. Additionally, The World Health Organization International Trials Registry Platform was queried on June 23, 2017. Eligible studies reported thromboembolic events among individuals with prostate cancer exposed to ADT vs a lesser-exposed group. Five hundred sixty-nine unique studies were identified with 65 undergoing full-text review. We utilized the Meta-analysis of Observational Studies in Epidemiology statement guidelines and the Cochrane Review Group's data extraction template. Study quality was evaluated by Newcastle-Ottawa Scale criteria. We conducted random-effects meta-analyses to calculate summary statistic risk ratios and 95% confidence intervals. Heterogeneity was quantified using the I² statistic. Small study effects were evaluated using Begg and Egger statistics.

In 10 studies “ADT without estrogen” increased the risk of thromboembolic events (risk ratio [RR] 1.43, 95% confidence interval [CI] 1.15-1.77, P = .001). In 9 studies estrogen therapy alone was associated with an increased risk of thromboembolic events (RR 3.72, 95% CI 1.78-7.80, P <.001). We found an increased risk of thromboembolic events from ADT use without estrogen when limited to localized disease (RR 1.10, 95% CI 1.05-1.16, P <.001). Heterogeneity was resolved in those studies examining localized disease. There was no evidence of small study effects.

The currently available evidence suggests that ADT without estrogen is associated with an increased the risk of thromboembolic events.