General Practitioner Sex and Documented Cancer Prevalence in German Primary Care: A Matched Cross-Sectional Study

Background/Objectives: General practitioner’s (GP) sex has been associated with differences in consultation behaviour, preventive care, and physical examination practices. It remains unclear whether these differences translate into variation in documented cancer diagnoses in primary care. This study examined associations between GP sex and documented cancer prevalence across a broad range of malignancies in Germany. Methods: This retrospective cross-sectional study used data from the IQVIA™ Disease Analyzer database (IQVIA, Frankfurt am Main, Germany), a representative German outpatient database. Individuals aged 18 years and older who attended one of 1182 general practices in 2025 were assigned to the practice they consulted and matched 1:1 by propensity score on patient sex, age, insurance type, and practice size. Thirteen ICD-10 cancer categories were analysed, with GP sex as the independent variable (male GP sex as the reference category), stratified by patient sex, using generalized estimating equations (GEEs) with the practice as the clustering unit and cluster-robust standard errors as the primary analysis; generalized linear mixed models with a practice-level random intercept were fitted as a sensitivity analysis. Absolute prevalence differences per 1000 patients were estimated with cluster-robust linear models. Two-sided p-values < 0.05 were considered statistically significant, and Bonferroni and Benjamini–Hochberg false discovery rate (FDR) corrections were applied to a pre-specified family of 23 models. Results: A total of 1,204,254 individuals seen by female GPs (mean age 53.3 [standard deviation, SD, 19.8] years; 54.8% female) and 1,204,254 individuals seen by male GPs (mean age 53.7 [SD 19.8] years; 55.2% female) were included. In the cluster-adjusted (GEE) models, female GP sex was associated with higher odds of documented skin cancer in female patients (odds ratio [OR] 1.23, 95% confidence interval [CI] 1.11–1.35; absolute difference 1.15 per 1000 patients, 95% CI 0.58–1.73), which remained significant after both FDR and Bonferroni correction; in male patients the association was weaker and did not remain significant after correction (OR 1.14, 95% CI 1.03–1.26). In exploratory analyses, the association was confined to non-melanoma skin cancer (female patients OR 1.27, 95% CI 1.14–1.42) and to patients aged 35 years and older. The inverse association for mesothelial and soft tissue cancer seen in unadjusted models was no longer statistically significant after accounting for practice-level clustering (female patients OR 0.75, 95% CI 0.43–1.31; male patients OR 0.75, 95% CI 0.45–1.25). No statistically significant associations were observed for breast, digestive, genital organ, haematological, or other cancer types. Conclusions: After accounting for clustering at the practice level, female GP sex was associated with a higher prevalence of documented skin cancer—most robustly among female patients—whereas associations for other malignancies, including mesothelial and soft tissue cancer, were not statistically significant. The design cannot distinguish differences in examination from differences in documentation. These findings have implications for the interpretation of routine cancer data and indicate that practice-level factors, and the clustering of patients within practices, should be considered when documented cancer prevalence is analysed in primary care data.