OBJECTIVES: The impact of sex inequities in healthcare may be magnified in oncology where patients and physicians often navigate life-limiting prognoses. We aimed to examine the associations among patient-physician sex concordance, treatment practices, and cancer outcomes.

METHODS: This was a population-based, retrospective cohort study of adults diagnosed with stage II-IV colon or lung cancer in 2013-2020 in Alberta, Canada and referred to an oncologist. We classified patient-physician dyads as sex-concordant (female-female, male-male) or discordant (female-male, male-female). We analysed time-to-event data using Kaplan-Meier methods and associations with Cox and logistic regression.

RESULTS: We identified 11,830 patients, of whom 49% were female and 50% were in sex-concordant patient-physician dyads. The median age was 68 years, 64% had lung cancer, and 51% had stage IV disease. In sex-concordant and discordant dyads, respectively, median overall survival (OS) was 19.1 and 20.9 months (p = 0.06) while median cancer-specific survival (CSS) was 23.3 and 25.2 months (p = 0.28). In multivariable analysis, sex-concordance was not significantly associated with OS or CSS in the overall cohort and in female patients. Among male patients, however, sex-discordance was significantly associated with lower OS (HR, 1.10; 95% CI, 1.02-1.17) and CSS (HR, 1.11; 95% CI 1.03-1.20), driven by differential outcomes in stage IV disease. Older age, higher comorbidity, lung cancer, and advanced stage correlated with worse outcomes in all models. Among patients with stage II-III disease, 22% received adjuvant systemic anti-cancer therapy (SACT) and of those with stage IV disease, 63% received SACT. Sex concordance was not significantly associated with SACT use or time to SACT initiation.

CONCLUSIONS: Sex concordance between patients and oncologists did not generally correlate with treatments patterns. However, male patients treated by female physicians had worse outcomes compared to those treated by male physicians. Cancer outcomes may be prone to the effects of sex bias in specific patient-physician relationships.