Comparative Survival Associated With Use of Targeted vs Nontargeted Therapy in Medicare Patients With Metastatic Renal Cell Carcinoma

Abstract

Targeted therapies for advanced renal cell carcinoma (RCC) have shown increased tolerability and survival advantages over older treatments in clinical trials, but understanding of real-world survival improvements is still emerging. To compare overall and RCC-specific survival associated with use of targeted vs nontargeted therapy for metastatic RCC. This retrospective cohort study used Surveillance, Epidemiology, and End Results-Medicare data from 2000 to 2013 to examine patients with stage IV (distant) clear cell RCC at the time of diagnosis who received any targeted or nontargeted therapy. A 2-stage residual inclusion model was fitted to estimate the survival advantages of targeted treatments using an instrumental variable approach to account for both measured and unmeasured group differences. Data analyses were conducted from July 24, 2017, to April 4, 2019. Targeted therapy (study group) or nontargeted therapy (control group). Overall survival and RCC-specific survival, defined as the interval between the date of first drug treatment and date of death or end of the observation period. The final sample included 1015 patients (mean [SD] age, 71.2 [8.1] years; 392 [39%] women); 374 (37%) received nontargeted therapy and 641 (63%) received targeted therapy. The targeted therapy group had a greater percentage of disabled patients (ie, those <65 years old who were eligible for Medicare because of disability) and older patients (ie, those ≥75 years old) and higher comorbidity index and disability scores compared with the nontargeted therapy group. Unadjusted Kaplan-Meier survival curves showed higher overall survival for targeted vs nontargeted therapy (log-rank test, χ21 = 5.79; P = .02); median survival was not statistically significantly different (8.7 months [95% CI, 7.3-10.2 months] vs 7.2 months [95% CI, 5.8-8.8 months]; P = .14). According to the instrumental variable analysis, the median overall survival advantage was 3.0 months (95% CI, 0.7-5.3 months), and overall survival improvements associated with targeted therapy vs nontargeted therapy were statistically significant: 8% at 1 year (44% [95% CI, 39%-50%] vs 36% [95% CI, 30%-42%]; P = .01), 7% at 2 years (25% [95% CI, 20%-30%] vs 18% [95% CI, 13%-23%]; P = .009), and 5% at 3 years (15% [95% CI, 11%-19%] vs 10% [95% CI, 6%-13%]; P = .01). Receipt of targeted therapy was associated with a lower hazard of death compared with nontargeted therapy (overall survival hazard ratio, 0.78 [95% CI, 0.65-0.94]; RCC-specific survival hazard ratio, 0.77 [95% CI, 0.62-0.96]). Targeted therapies were associated with modest survival advantages despite a treatment group with more medical complexity, likely reflecting appropriateness for an expanded population of patients. As advances in cancer treatment continue, rigorous methods that account for unobserved confounders will be needed to evaluate their real-world impact on outcomes.