Who participates in myeloma trials? clinical and geographic predictors of access and outcomes in British Columbia, Canada.

Abstract Introduction: Clinical trials (CTs) are essential for advancing evidence-based treatment in multiple myeloma (MM), offering patients early access to novel therapies. British Columbia (BC), a geographically large province, more than twice the size of France, has centralized CTs in major urban centers, potentially limiting access for patients in rural areas. The impact of geographic, clinical, and socioeconomic factors (SEFs) on CT participation and outcomes remains poorly understood. This study evaluated predictors of CT participation and its association with overall survival (OS) in a real-world MM cohort in BC. Methods: We conducted a single-center retrospective cohort study of MM patients aged >18 diagnosed between January 2000 and December 2023 who received systemic therapy. CT participation was defined as enrollment in any interventional or observational study providing care beyond standard treatment. Data were collected from a local MM database and chart review. Variables included demographics, SEFs, ECOG performance status, comorbidities, and OS. Univariate and multivariate Cox proportional hazards models were used to identify predictors of CT participation and OS. Results: Among 599 patients, 80 (13.4%) participated in a CT. Compared to non-participants, CT participants lived closer to the center (mean 101 km vs 174 km, p = 0.0002), were more likely to reside in urban areas (90.0% vs 69.6%, p = 0.0002), had better ECOG performance status (p = 0.0006), and fewer comorbidities (mean 1.46 vs 1.83, p = 0.04). No significant differences were observed in income, SES, marital status, ISS stage, or ASCT receipt. On univariate analysis, CT participation was associated with longer OS (HR 0.69; median 121.7 vs 93.9 months). Other significant predictors of OS included younger age (continuous variable, HR 1.05, p < 0.0001), employed status (HR 0.64, p < 0.0001), ECOG status (HR range 1.98-21.14, p < 0.0001), and ASCT (HR 0.40, p < 0.0001). In multivariate analysis, CT participation showed a non-significant trend toward improved OS (HR 0.73, p = 0.07), while age, ECOG status, and ASCT remained independent predictors. Conclusion: In this real-world cohort, CT participants were more likely to reside in urban areas, live closer to the treatment center, and have better performance status and fewer comorbidities. These findings suggest that geographic distance and clinical fitness are key barriers to trial participation, while income and SES were not as influential. Although CT participation was associated with longer OS in univariate analysis, this effect did not reach statistical significance after adjustment, though a favorable trend remained. These results underscore the need to expand trial access to rural and comorbid patients and support prospective studies using matched cohorts to better understand the impact of CT participation on outcomes.