Presentation Authors: Nermarie Velazquez*, Audrey Renson, Stella K. Kang, William C. Huang, New York, NY, Marc A. Bjurlin, Chapel Hill, NC
Introduction: The natural history of observed large (T1b [4-7cm] or T2a [>7-10cm]) kidney cancers is not well known. Both increasing size and histologic subtype of renal cell carcinoma (RCC) may impact survival of those patients with large kidney cancers being observed. The aim of our study was to determine the overall survival of patients with biopsy proven, T1b and T2a RCC.
Methods: We queried the National Cancer Data Base for the years 2004 through 2015 for patients with biopsy proven RCC which was greater than 4cm and who were managed non-operatively. OS was estimated by Kaplan-Meier curves based on histologic subtype. Cox proportional regression models were used to determine whether histologic subtypes predicted survival for each stage. Our adjusted model used inverse probability weights for possible confounding factors including age, sex, race/ethnicity, insurance status, median income, proportion without high school diploma, urbanicity, Charslon-Deyo index, and tumor grade.
Results: A total of 645 patients with T1b and 81 with T2a were identified with biopsy confirmed RCC. Of those 445 were clear cell, 202 papillary, 70 chromophobe, 8 sarcomatoid, and 1 collecting duct . In patients with T1b kidney cancers Kaplan-Meier curves demonstrated a difference in OS between histologic subtypes (p=0.021, Figure 1) with a greater median OS for patients with chromophobe (61.2 months, HR 0.68 , p=0.142) and papillary (42.4 months, HR 0.77, p=0.098) compared to clear cell (38.3 months, reference group). However, in patients with T2a kidney cancers there was no significant difference in survival based on histology (p =0.314, Figure 2).
Conclusions: Histologic subtype appears to influence OS in observed T1b RCC where both chromophobe and papillary demonstrate better OS compared to clear cell. However, no such differences are noted for T2a tumors. Perhaps at higher stages tumor size outweighs histological variant although our study likely was underpowered in this cohort given the rarity of observing these larger masses. This observational study supports the utility of renal biopsy to inform decision making in T1b renal masses although further prospective studies remain necessary.