The current management of small renal masses

Textural differences in apparent diffusion coefficient between low- and high-stage clear cell renal cell carcinoma

OBJECTIVE

The purpose of this article is to evaluate differences in texture measures on apparent diffusion coefficient (ADC) maps between low- and high-stage clear cell renal cell carcinomas (RCCs).

MATERIALS AND METHODS

In this retrospective study, 61 patients with clear cell RCC at pathologic examination and who underwent preoperative MRI with diffusion-weighted imaging were included. Clear cell RCCs were clinically staged on review of preoperative MRI by a board-certified radiologist blinded to the pathologic findings. Whole lesions were segmented on ADC maps by two readers independently, from which first-order texture features (i.e., mean and skewness) and second-order texture features (i.e., cooccurrence matrix measures) were calculated. Texture metrics were compared between low- and high-stage clear cell RCC.

RESULTS

In 61 patients, there were 62 clear cell RCCs (33 low stage [stages I and II] and 29 high stage [stages III and IV]) at pathologic examination. Staging accuracy of qualitative interpretation was 100% for low-stage lesions and 37.9% (11/29) for high-stage lesions. There was no statistically significant difference in mean ADC between high- and low-stage clear cell RCCs (1.77×10(-3) vs 1.80×10(-3) mm2/s; p=0.7). However, high-stage clear cell RCCs were larger (6.96±2.93 vs 3.49±1.57 cm; p<0.0001) and had statistically significantly (p≤0.0001) higher ADC skewness (0.02±0.33 vs -0.52±0.65) and cooccurrence matrix correlation (0.64±0.11 vs 0.49±0.13). Multivariate logistic regression identified size, skewness, and cooccurrence matrix correlation as significant independent predictors of high stage (AUC=0.92). Interreader correlation in texture metrics ranged from 0.82 to 0.89.

CONCLUSION

First- and second-order ADC texture metrics differ between low- and high-stage clear cell RCCs. A model that includes size and ADC texture measures may help to stage clear cell RCCs noninvasively.

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

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.