Upper urinary tract urothelial carcinoma (UTUC), which arises from the urothelium of the renal calyx to the ureter, accounts for 10% of all urothelial carcinoma [1]. The current gold standard therapy for UTUC is radical nephroureterectomy (RNU) with bladder cuff excision [2,3]. In advanced stages, the 5-year cancer-specific survival is low; <50% for pT2 and pT3 tumors and <10% for pT4 tumors [4], [5], [6]. Approximately 60% of patients are diagnosed with muscle invasion (pT2 or higher) at the initial presentation, which may be advantageous for perioperative treatment [2,7]. Therefore, identifying prognostic factors that accurately predict outcomes is crucial for determining the appropriate treatment for patients with UTUC.

Cancer progression and cancer-related mortality result from a complex interplay between tumor pathogenesis and the host immune response [8,9]. Although several clinicopathologic factors have been utilized for prognostic assessment of UTUC following RNU, they predominantly reflect tumor-related conditions rather than host-related factors [10], [11], [12]. Systemic inflammatory reactions and chronic nutritional status are well-established host-related mechanisms associated with cancer development and progression [13,14]. Due to the importance of blood-based calculation of inflammatory signatures from routine pre-operative laboratory tests, several attempts have been made to assess the prognostic role of biomarkers such as the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and C-reactive protein (CRP) in various malignancies [15]. CRP, in particular, offers advantages in terms of standardized measurement and reliability, as it reflects acute phase inflammation [16]. Hypoalbuminemia is recognized as a reflection of both chronic systemic inflammatory response and nutritional status [17]. Therefore, the CRP to albumin ratio (CAR) has the potential to capture both acute and chronic systemic inflammatory responses and cancer-related cachexia. Consequently, the prognostic role of CAR has been actively investigated in the pre-treatment setting of several malignancies [18,19]. However, few studies have examined the prognostic significance of CAR in UTUC.

Herein, we aimed to examine the prognostic value of CAR on progression-free survival (PFS) and cancer-specific survival (CSS) in patients with UTUC after RNU.