KIM-1 in Advanced Papillary and Clear Cell Renal Cell Carcinoma

Kidney injury molecule 1 (KIM-1) is a promising biomarker in adjuvant clear cell renal cell carcinoma (ccRCC), but its relevance in advanced ccRCC or papillary RCC (pRCC) remains unclear. CALYPSO (NCT02819596) was a prospective, multi-arm trial that evaluated durvalumab alone or in combination with tremelimumab or savolitinib in metastatic ccRCC and pRCC. Circulating KIM-1 levels were measured at baseline and on-treatment. The primary endpoint was to explore if KIM-1 levels were raised in pRCC. Analyses were exploratory and p values were nominal. KIM-1 was measured in 123 patients with ccRCC and 31 patients with pRCC. Higher median concentrations occurred in pRCC compared to ccRCC (7835 vs 5470 pg/ml, p = 0.05). Reductions in KIM-1 levels occurred with systemic therapy in both ccRCC and pRCC (-59.2% and -32% respectively). In pRCC, radiological responders had significantly lower baseline KIM-1 levels (p = 0.025). In ccRCC, high baseline KIM-1 levels were associated with significantly shorter overall survival (OS) (hazard ratio [HR] 1.77; 95% CI, 1.15-2.72; p = 0.01). Also, an increase in KIM-1 during therapy was linked to worse progression-free survival (HR 1.7; 95% CI, 1.13-2.58; p = 0.01) and OS (HR 1.95; 95% CI, 1.23-3.08; p = 0.004) in ccRCC. This exploratory analysis supports the utility of KIM-1 in advanced ccRCC and pRCC.