Objective: Renal cell carcinoma (RCC) patients in clinical T1 RCC generally exhibit a favorable prognosis. Guidelines recommend partial nephrectomy (PN), also for cT1b RCCs. Despite a favorable prognosis, there remains risks for upstaging and recurrence for cT1b RCC patients, and the preference for PN has been questionable. Clinical and morphological variables and overall survival (OS) were characterized in a national real-world population.

Methods: Data from the the National Swedish Kidney Cancer Register 2005-2014, with non-metastatic cT1bRCC patients treated surgically and having ≥5 years potential follow-up were included (n = 2006). Patients gender, age, stage, tumor size, RCC type, local and distant tumor recurrence were evaluated.

Results: Among 2006 patients (1219 males, 787 females; mean age 66 years), 1705 underwent radical nephrectomy (RN), and 301 PN. Upstage from cT1b to pathological T3a occurred in 304 (15%) patients. Recurrent disease was diagnosed in 318 (16%) patients, with higher rates in pT3a (25%) compared to pT1b (14%). There was no significant difference in disease recurrences observed between the surgical techniques. Factors associated with increased recurrence risk included age, T-stage, N-stage, and tumor size, while papillary and chromophobe RCCs were associated with decreased risk. Patients with pT3a RCC had a worse 5-year OS rate (67%) compared with pT1b (83%; P < .001, log-rank test). In adjusted analyses, age, tumor size, pT-stage, and pNstage were associated with OS, while treatment with PN was non-inferior compared with RN (hazard ratio 0.91, 95% CI: 0.71-1.45, P = .431).

Conclusion: Patients with clinical T1b RCCs face a non-negligible risk for tumor upstaging, disease recurrence, and decreased OS. The adjusted analyses showed that PN was non-inferior to RN, supporting the recommendation to offer PN.