Drug exposure definitions reported in real-world evidence studies on oncology medicines in patients with colorectal cancer: a scoping review

Background: Defining, measuring, and reporting exposure in real-world data are important for the valid generation and interpretation of real-world evidence (RWE). This is especially challenging for oncology medicines, due to complicated treatment regimens and adjustments in dose and/or schedule. This scoping review aims to assess the reporting of drug exposure definitions for oncology medicines in RWE studies, using colorectal cancer (CRC) as a case study. Methods: We searched PubMed and Embase for RWE studies assessing clinical outcomes of cyclically administered oncology medicines in patients with CRC, published in 2023-2024. We extracted publication characteristics, study characteristics, and exposure variables. We calculated a drug exposure reporting score (0-7), composed of active substance, dose, dosing schedule, number of cycles, treatment episode length, and drug exposure start/end. We exploratively compared characteristics of studies with a high and low score. Results: Of the 61 included studies, 59% used hospital data, and 36.1% used drug administration data. Most studies (83.6%) reported the start of drug exposure, and 34.4% reported the end of drug exposure. Median drug exposure reporting score was 3.0 (interquartile range 2.0-4.0). Studies with a high score were 4.6 times more often published in an oncology journal and reported use of guidelines for observational studies 1.8 times more often than studies with a low score. Conclusion: Definitions of drug exposure are often underreported in RWE studies on oncology medicines. Lack of clarity concerning oncological drug exposure complicates the assessment of the methodological quality and reproducibility and may affect the interpretation of the association between oncology medicines and clinical outcomes.