Extent of lymphadenectomy does not improve the survival of patients with renal cell carcinoma and nodal metastases: biases associated with the handling of missing data.
Academic Article
Overview
abstract
UNLABELLED: WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: A recent population-based analysis suggested a potential survival benefit with respect to performing lymph node dissection at nephrectomy in node-positive patients with RCC. The findings of the present study failed to corroborate the association of a survival benefit with the performance of lymph node dissection at nephrectomy. OBJECTIVE: Previous studies showed no survival benefit with respect to performing lymph node dissection (LND) at nephrectomy, whereas a recent population-based analysis suggested otherwise, although the latter relied on imputation. To reconcile the findings of that study by critically evaluating the handling of missing data. PATIENTS AND METHODS: Study participants comprised patients diagnosed with non-metastatic renal cell carcinoma (RCC) of all stages who underwent LND at nephrectomy (n = 10 596). Multivariable Cox regression models were performed to predict cancer-specific mortality (CSM), where the primary variable of interest was the extent of LND. To examine differences in approaches with respect to handling missing data, separate analyses were performed: (i) imputed population; (ii) exclusion of patients with missing data; and (iii) inclusion of patients with missing data as a sub-category. RESULTS: Overall, 2916 (28%) patients had missing tumour grade. In multivariable analyses, our findings showed that increasing the extent of LND was associated with a significant protective effect on CSM in patients with pN1 after imputation (hazard ratio [HR], 0.82; P = 0.04). By contrast, the extent of LND was no longer significantly associated with a lower risk of CSM after excluding patients with a missing tumour grade (HR, 0.83; P = 0.1) or when including patients with missing tumour grade as a sub-category (HR, 0.82; P = 0.05). CONCLUSIONS: The findings of the present study failed to corroborate the association of a survival benefit with increasing extent of LND at nephrectomy. The different methodologies employed to account for missing data may introduce important biases. Such considerations are non-negligible with respect to the interpretation of results for investigators who rely on administrative cohorts.
