Renal Cell Carcinoma: Comparison between Variant Histology and Clear Cell Carcinoma across All Stages and Treatment Modalities

PURPOSE: We evaluated stage at presentation and cancer specific mortality according to variant histology relative to clear cell renal cell carcinoma. MATERIALS AND METHODS: Within the Surveillance, Epidemiology, and End Results registry (2001-2016) we identified variant histology and clear cell renal cell carcinoma cases. Cumulative incidence plots, multivariate Cox regression models matched for stage, grade and other patient characteristics addressed cancer specific mortality. Subgroup analyses relied on inverse probability treatment weighting according to nephrectomy type. RESULTS: Of all 69,785 patients with renal cell carcinoma 2,495 harbored variant histology (3.6%). Of patients with variant histology 70.1% (1,748) harbored sarcomatoid vs 11.2% (280) collecting duct vs 7.6% (190) mesenchymal vs 3.8% (94) neuroendocrine vs 2.9% (72) renal medullary vs 2.5% (62) mucinous tubular and spindle cell, and 2.0% (49) rhabdoid tumors. All patients with variant histology exhibited more advanced TNM stage at diagnosis than clear cell renal cell carcinoma, except for mucinous tubular and spindle cell. After matching with G4 clear cell renal cell carcinoma, collecting duct (multivariate HR 1.6, p <0.01), sarcomatoid (HR 1.8, p <0.01), renal medullary (HR 1.7, p=0.1) and rhabdoid variant histology (HR 1.5, p=0.1) showed higher cancer specific mortality than clear cell renal cell carcinoma. No cancer specific mortality differences were recorded for mesenchymal, neuroendocrine and mucinous tubular and spindle cell variant histology. In nephrectomy subgroup higher cancer specific mortality was recorded after partial nephrectomy than radical nephrectomy in sarcomatoid variant histology after inverse probability treatment weighting and multivariate adjustment (HR 1.2, p=0.02). CONCLUSIONS: TNM stage at diagnosis is universally more advanced in patients with variant histology, except for mucinous tubular and spindle cell. Cancer specific mortality is higher in collecting duct, sarcomatoid, rhabdoid and renal medullary variant histology, but not in other variant histology. Partial nephrectomy is associated with worse survival in sarcomatoid variant histology but could not be assessed in other variant histology due to small sample size.