Survival pattern of metastatic renal cell carcinoma patients according to WHO/ISUP grade: a long-term multi-institutional study

The World Health Organization/International Society of Urological Pathology (WHO/ISUP) grading of renal cell carcinoma (RCC) is classified from grade 1–4, regardless of subtype. The National Comprehensive Cancer Network (NCCN) guidelines (2022) state that if there is an adverse pathological feature, such as grade 3 or higher RCC in stage 1 patients, more rigorous follow-up imaging is recommended. However, the RCC guidelines do not provide specific treatment or follow-up policies by tumor grade. Therefore, this study attempted to find out whether tumor grade affects survival rates in patients with metastatic RCC. The Korean Renal Cancer Study Group (KRoCS) database includes 3108 patients diagnosed with metastatic RCC between September 1992 and February 2017, with treatment methods, progression, and survival data collected from 11 tertiary hospitals. To obtain information on survival rates or causes of death, we utilized the Korea National Statistical Office database and institutional medical records. Data were accessed for research purpose on June, 2023. We then reviewed these sources to gather comprehensive and reliable data on the outcomes of our study cohort. This database was retrospectively analyzed, and out of 3108 metastatic RCC patients, 911 had been identified as WHO/ISUP grade. Grades were classified into either a low-grade (WHO/ISUP grade 1–2) or a high-grade group (WHO/ISUP grade 3–4). The patients were then analyzed related to progression and overall survival (OS). In metastatic clear cell RCC patients, the 1-year OS rate was 69.4% and the median OS was 17.0 months (15.5–18.5) followed up to 203.6 months. When comparing the patient groups, 119 low-grade and 873 high-grade cases were identified. No baseline difference was observed between the two groups, except that the high-grade group had a higher ECOG 1 ratio of 50.4% compared with 34.5% for the low-grade group ( p = 0.009). There was a significant difference in OS between high-grade and low-grade groups. OS was 16.0 months (14.6–17.4) in the high-grade group and 28.0 months (21.1–34.9) in the low-grade group ( p < 0.001). However, there was no difference in progression-free survival (PFS) rates with 9.0 months (8.0–10.0) for the high-grade group and 10.0 months (6.8–13.2) for the low-grade group ( p = 0.377) in first-line treatment. In multivariable analysis, WHO/ISUP grade was a risk factor (HR = 1.511[1.135–2.013], p = 0.005) that influenced the OS. In conclusion, WHO/ISUP grade is a major data source that can be used as a ubiquitous marker of metastatic RCC in pre-IO era. Depending on whether the RCC is high or low grade, the follow-up schedule will need to be tailored according to grade, with higher-grade patients needing more active treatment as it can not only affect the OS in the previously known localized/locoregional recurrence but also the metastatic RCC patient.