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Keywords:

  • lymph node dissection;
  • nephrectomy;
  • renal cell carcinoma;
  • survival;
  • extent

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.