Predictive Factors Affecting Metastasis of Small Renal Mass and Its Prognostic Analysis

BACKGROUND: The incidence of small renal mass (SRM) increases, and the prognosis of SRM is poor once metastasized. Therefore, we conducted this study to assess the clinical and pathological characteristics of SRM to determine the risk factors that influence the metastasis and prognosis of SRM. METHODS: A small renal mass is defined as a solid tumor mass with the largest diameter of 4 cm or less on the pathological diagnosis. The metastasis is confirmed by imaging or pathological examination. We retrospectively included 40 patients with metastatic SRM (mSRM) treated in the department of urology of Peking University Third Hospital from October 2002 to October 2020. Meanwhile, 358 patients with nonmetastatic SRM treated in our hospital from January 2015 to December 2017 were selected as controls. Clinicopathologic features were compiled. RESULTS: Multivariate logistic regression analysis showed that age (P = .027, odds ratio [OR] = 1.037, 95% confidence interval [CI] 1.004-1.070), clinical symptoms (P < .001, OR = 4.311, 95% CI 1.922-9.672), World Health Organization/International Society of Urological Pathology (WHO/ISUP) nuclear grade 3/4 (P = .004, OR = 7.637, 95% CI 1.943-30.012; P = .004, OR = 20.523, 95% CI 2.628-160.287), and lymphatic invasion (P = .030, OR = 15.844, 95% CI 1.314-191.033) were risk factors for distant metastasis of SRM. Once metastasis occurs, the prognosis of SRM is poor. Multivariate Cox regression analysis of the prognosis of mSRM showed that age (P = .016, hazard ratio [HR] = 1.125, 95% CI 1.022-1.239), preoperative serum creatinine (P = .041, HR = 1.003, 95% CI 1.000-1.005), vascular invasion (P = .041, HR = 1.003, 95% CI 1.000-1.005), and metastasis (P < .001, HR = 24.069, 95% CI 4.549-127.356) were risk factors for overall survival (OS), and only metastasis (P < .001, HR = 9.52, 95% CI 5.43-16.7) was a risk factor for progression-free survival (PFS) of SRM. CONCLUSIONS: SRM with advanced age, clinical symptoms, high pathological nuclear grade, and lymphatic invasion are more likely to have distant metastasis. And SRM with older age, poor preoperative basic renal function, pathological vascular invasion, and metastasis have worse OS.