Defining and Measuring Adherence in Observational Studies Assessing Outcomes of Real-world Active Surveillance for Prostate Cancer: A Systematic Review

Context: Evidence-based guidelines for active surveillance (AS), a treatment option for men with low-risk prostate cancer, recommend regular follow-up at periodic intervals to monitor disease progression. However, gaps in monitoring can lead to delayed detection of cancer progression, leading to a missed window of curability.

Objective: We aimed to identify the extent to which real-world observational studies reported adherence to monitoring protocols among prostate cancer patients on AS. When reported, we sought to characterize definitions of adherence.

Evidence acquisition: We systematically reviewed observational studies assessing outcomes of prostate cancer patients on AS, published before March 22, 2019 in PubMed, Embase, and CENTRAL. Adherence definitions were considered time bound if they included prespecified time and binary if adherence was assessed but did not specify a time interval. We assessed study quality using the Strengthening the Reporting of Observational Studies in Epidemiology checklist.

Evidence synthesis: Forty-five studies met our inclusion criteria. Eleven studies did not report any data on adherence to AS protocols. Twenty-five studies did not explicitly measure adherence, but provided relevant data (eg, number of patients who received a repeat biopsy). Six studies reported adherence using a time-bound definition, while three studies used a binary definition. Twenty-three studies provided information on patients lost to follow-up.

Conclusions: Most studies reporting outcomes of patients on AS did not measure or report adherence. When reported, adherence was often not time specific. As some AS patients will benefit from maintaining a window of curability, clinical practices and future studies should track and report adherence and associated factors.

Patient summary: We reviewed real-world observational studies examining outcomes of prostate cancer patients on active surveillance. Most studies did not clearly define or report adherence to monitoring protocols, which is important to consider for appropriate disease management.