Long-term survival following partial vs radical nephrectomy among older patients with early-stage kidney cancer

Abstract

Context: Although partial nephrectomy is the preferred treatment for many patients with early-stage kidney cancer, recent clinical trial data, which demonstrate better survival for patients treated with radical nephrectomy, have generated new uncertainty regarding the comparative effectiveness of these treatment options.

Objective: To compare long-term survival after partial vs radical nephrectomy among a population-based patient cohort whose treatment reflects contemporary surgical practice.

Design, setting, and patients: We performed a retrospective cohort study of Medicare beneficiaries with clinical stage T1a kidney cancer treated with partial or radical nephrectomy from 1992 through 2007. Using an instrumental variable approach to account for measured and unmeasured differences between treatment groups, we fit a 2-stage residual inclusion model to estimate the treatment effect of partial nephrectomy on long-term survival.

Main outcome measures: Overall and kidney cancer-specific survival.

Results: Among 7138 Medicare beneficiaries with early-stage kidney cancer, we identified 1925 patients (27.0%) treated with partial nephrectomy and 5213 patients (73.0%) treated with radical nephrectomy. During a median follow-up of 62 months, 487 (25.3%) and 2164 (41.5%) patients died following partial or radical nephrectomy, respectively. Kidney cancer was the cause of death for 37 patients (1.9%) treated with partial nephrectomy, and 222 patients (4.3%) treated with radical nephrectomy. Patients treated with partial nephrectomy had a significantly lower risk of death (hazard ratio [HR], 0.54; 95% CI, 0.34-0.85). This corresponded with a predicted survival increase with partial nephrectomy of 5.6 (95% CI, 1.9-9.3), 11.8 (95% CI, 3.9-19.7), and 15.5 (95% CI, 5.0-26.0) percentage points at 2, 5, and 8 years posttreatment (P < .001). No difference was noted in kidney cancer-specific survival (HR, 0.82; 95% CI, 0.19-3.49).

Conclusion: Among Medicare beneficiaries with early-stage kidney cancer who were candidates for either surgery, treatment with partial rather than radical nephrectomy was associated with improved survival.

Figure 1

Kaplan-Meier estimates of all-cause and kidney cancer-specific mortality for patients treated with partial versus radical nephrectomy. Kaplan-Meier mortality estimates are compared using the log-rank test. The y-axis regions shown in blue indicate the range from 0% to 20%.

Figure 2

Proportion of patients treated with partial or radical nephrectomy according to differential distance category. The reported chi-squared statistic is for the unadjusted association between differential distance and type of surgical treatment. Error bars depict the 95% confidence interval for each proportion. The number of patients within each differential distance category is also reported.

Figure 3

Predicted survival probabilities at 2-, 5-, and 8-years after treatment with partial or radical nephrectomy. Probability estimates are derived from a two-stage residual inclusion model, adjusting for patient demographics, cancer severity, surgical approach, and the occurrence of post-operative complications. Statistical significance was determined by assessing the predicted marginal difference in survival between treatment groups at each time point. Error bars depict the 95% confidence interval for each survival estimate.