Abstract B036: Prevalence of non-clear cell renal cell carcinoma based on new WHO classification: Results from a multicenter BUCARE Study

Abstract Background: The reported prevalence of non-clear cell renal cell carcinoma (nccRCC) has varied across studies for years, partially due to evolving WHO classifications and improvements in pathological diagnosis. These changes may have impacted the true prevalence of nccRCC in daily practice. The aim of this large multicenter analysis was to accurately estimate the prevalence of nccRCC in order to understand the relevance of the problem. Methods: A retrospective analysis was conducted at 9 cancer centers across southern, central, and eastern Russia (Chelyabinsk, Ekaterinburg, Kazan, Khabarovsk, Krasnodar, Omsk, Orenburg, Ufa, and Yuzhno-Sakhalinsk). These regions have only one comprehensive cancer center and accumulate all RCC patients. Patients diagnosed with RCC between 2022 and 2023, confirmed histologically with detailed pathological descriptions, were included. Data were collected via an anonymized online registry. The primary outcome was the period prevalence of nccRCC, defined as the proportion of nccRCC cases over a 12-month period. Results: A total of 2,835 adult patients were analyzed, with a mean of 315 patients per region annually. All cases had confirmed RCC subtypes. Of these, 540 patients were diagnosed with nccRCC, yielding a period prevalence of 19.05%. The most common histological subtypes were papillary RCC (7.5%) and chromophobe RCC (6%). Further details on the prevalence of other nccRCC subtypes will be presented at the congress. Conclusions: The study findings confirm previously reported prevalence rates of nccRCC. Notably, any changes in prevalence appear to be associated with shifts within nccRCC subtypes due to the new WHO classification, rather than significant differences in comparison to clear cell RCC. Ongoing analysis will provide further insights into these patterns. Citation Format: Vladislav Petkau, Dmitrii Shemetov, Sufia Safina, Olga Novikova, Alla Goryainova, Evgeny Kopyltsov, Makhabbat Murzalina, Alexander Sultanbaev, Elvira Parsadanova, Grigory Raskin, Ilya Tsimafeyeu. Prevalence of non-clear cell renal cell carcinoma based on new WHO classification: Results from a multicenter BUCARE Study [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Kidney Cancer Research: From Molecular Insights to Therapeutic Breakthroughs; 2026 Mar 13-16; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(5_Suppl_2):Abstract nr B036.