Association between frailty and incident cancer in newly diagnosed patients with rheumatoid arthritis

Rheumatoid Arthritis (RA) is associated with an increased risk of cancer, but the underlying risk factors remain poorly understood. Frailty is linked to an increased cancer risk in the general population and is more common among those with RA than those without it. We aimed to evaluate frailty as a risk factor for incident cancer in RA.

We used the Merative MarketScan databases from 2008 to 2022 to identify individuals with newly diagnosed RA using diagnosis codes and pharmacy records. Patients were categorized as frail or non-frail based on a claims-based frailty index. Incident cancer was identified using a validated algorithm in administrative claims data. Unadjusted and adjusted (for demographics, Charlson comorbidity index, and healthcare utilization) Cox proportional hazards models were created to obtain hazard ratios (HRs) and 95% confidence intervals (95% CIs).

Among 73,240 individuals with newly diagnosed RA, 4.1% were classified as frail. Incident cancer occurred more frequently and earlier among frail individuals (1.5% vs. 1.3%; median time to diagnosis: 312 vs. 561 days). Although frailty was associated with higher unadjusted cancer incidence (HR 1.5, 95% CI: 1.3-1.8), this association was attenuated after adjustment (HR 1.1, 95% CI: 0.9-1.4).

Frail patients with newly diagnosed RA had a higher unadjusted incidence of cancer, and shorter time to cancer diagnosis compared to non-frail patients. However, after adjusting for demographics, comorbidities and healthcare utilization, frailty alone was not an independent predictor of increased cancer risk in this relatively younger population with RA.