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Introduction: Complete or partial nephrectomy has been the predominant treatment for small incidentally diagnosed renal cell cancers (RCC). Some authors have suggested active surveillance as a treatment option, especially among patients with higher peri-operative risks, arguing that patients with small tumors have lower metastatic rates and better survival. The aim of the study is to test that argument for in a nationwide population registry.
Material and Methods: 791 histopathologically confirmed RCCs with known tumor size were diagnosed in Iceland between 1971 and 2005. Histological material and TNM staging were centrally reviewed. Synchronous metastases (SM) were recorded. Cancer-specific survival was calculated. Cubic-spline analysis compared size and metastatic rate. Multivariate analysis was applied to compare size to other known prognostic factors. Median follow-up was 6.7 years.
Results: With increased tumor size, synchronous metastasis (SM) rate increases in a non-linear fashion (10.6, 25.3, 35.2 and 49.6%) and five year survival decreases (86.1, 71.8, 53.0 and 32%) for tumors ≤ 4, 4.1-7.0, 7.1-10.0 and >10 cm, respectively. In multivariate analysis, size was a significant independent prognostic factor for synchronous metastasis (OR=1.08, p=0.01) and cancer specific survival (OR=1.09, p<0.01), while TNM stage was the strongest predictor of cancer specific survival (OR=2.58, p<0.01)
Conclusion: Size dose affect rates of SM and cancer related mortality. Size may aid in prognostication, but the TNM stage proves a superior marker. The relatively high (10.6%) propensity of tumors ≤ 4cm to metastasize should be kept in mind when advising active surveillance.