The role of immunotherapy treatment in non-clear cell renal cell carcinoma: An analysis of the literature

Non-clear cell renal cell carcinoma (nccRCC) is a heterogeneous group representing 15-30% of renal tumors. They are mostly excluded from immunotherapy trials due to their rarity and worse prognosis. This, alongside nccRCC misdiagnosis/misclassification, lack of immune-biomarker expression rate data, lack of homogeneous data reporting, the retrospective nature of many studies, small sample sizes, and the fact that high-grade evidence only stems from trials mostly addressing the clear cell subtype, result in poorly defined treatments. We thus reviewed available data from several clinical trials, retrospective studies, and meta-analyses on immunotherapy responses and their correlation with histological subtypes and prognostic biomarkers. The papillary and unclassified subtypes are the best candidate for immunotherapy, showing response rates up to similar to 35%. Chromophobe cancers, on the other end, have mostly null response rates. Cancers with sarcomatoid features respond very well to immunotherapy, regardless of their histology. Available data for translocation, medullary, collecting duct, and other nccRCCs are inconclusive. Regarding PD-L1, its expression correlates with better responses, but its prognostic value remains to be determined due to small sample sizes hindering direct statistical comparisons. It is necessary to involve a larger number of nccRCC patients and centers in clinical trials and report tumor response rates and PD-(L)1 and other markers' expression rates divided by nccRCC subtypes and not just for the whole cohorts. This will allow us to collect more robust data to best identify patients who can benefit from immunotherapy and ultimately define the standard of treatment.

Automated summary

Non-clear cell renal cell carcinoma (nccRCC) accounts for 15-30% of renal tumors and is excluded from immunotherapy trials due to its rarity and worse prognosis. Reviewed data from various sources suggest that papillary and unclassified subtypes show good response rates to immunotherapy, while chromophobe cancers have null response rates. Sarcomatoid features predict good response to immunotherapy regardless of histology. However, data for other nccRCC subtypes are inconclusive. It is important to involve more nccRCC patients in clinical trials and report response rates and biomarker expression rates by subtypes to define the standard of treatment.