They enrolled patients in a prospective AS registry between May 2005 and January 2016. These included patients with localized biopsy-proven small RCC ≤4cm, and followed with serial radiologic imaging. The primary end points analyzed were the conditional probability of survival and tumor growth over time. Specifically, they assess survival outcomes for patients who were on AS 2 years after the initial scan, as many prior studies have shown that patients destined to progress or require intervention often do so within the first 2 years.
A total of 272 patients were included in this analysis. Mean initial tumor size was 1.74 ± 0.77 cm and mean tumor size closest to the 2-year mark was 1.97 ± 0.83 cm, exhibiting slow growth kinetics. The likelihood of continued survival to 5 years improved after the 2-year landmark was reached. Patients with tumors <3cm who survived the first 2-years on AS had a 0.84-0.85 chance of surviving to 5 years, and if they survived 3 years, the probability of surviving to 5 years improved to 0.91. In their Table 1, where they break down survival probability at the 2,3,4, and 5-year mark for tumors <2 cm, 2-3 cm, and > 3-4, the peak 5-year survival probabilities (~95-96%) are achieved at the 4-year mark for tumors <3 cm.
Multivariable Cox proportional hazards analysis of survival revealed eGFR, Charlson comorbidity index (CCI), and tumor size of 3-4cm were significantly predictive of OS both at baseline and at 2-year mark (all p < 0.05). For both of these analyses, patients with a tumor size 3-4 cm were at a greater risk of non-RCC death (HR >3.5; p ≤ 0.001). A linear mixed effects model revealed slow tumor growth (beta: 0.12; p < 0.001) for tumors <3cm. Adjusted tumor size predictions disclosed parallel growth rates for small RCC of <2cm and 2-2.99cm with insignificant difference in growth rates (p = 0.969).
Based on these novel analyses, the authors conclude that the survival of patients with small RCC <3cm on AS improved after the initial 2 years, suggesting a role for re-counseling for those who survive to the 2-year landmark. Patient factors (renal function and CCI) were significantly associated with overall survival at baseline and at the 2-year landmark; however, no specific analysis was completed to assess association with cancer-specific survival.
While the method of analysis is novel, it merely confirms what was previously understood – patients destined to progress to treatment likely do so within the first 2 years of AS, and those that don’t are even less likely to progress. However, this does provide reassuring results to counsel patients with.
Presented by: Firas G. Petros, MD
Co-Authors: Aradhan Venkatesan MD², Diana Kaya MD², Chaan Ng MD², Bryan Fellman MS³, Jose Karam MD¹, Christopher Wood MD¹ and Surena Matin MD¹
Affiliation: ¹Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, Texas; ²Department of Diagnostic Radiology, The University of Texas MD Anderson Cancer Center, Houston, Texas; ³Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, twitter: @tchandra_uromd at the 18th Annual Meeting of the Society of Urologic Oncology, November 20-December 1, 2017 – Washington, DC