MP73-14 WHO WATCHES THE WATCHMEN?: SYSTEMATIC UNDERESTIMATION OF THE INCIDENCE OF KIDNEY CANCER IN CANCER REGISTRY DATA

Abstract

INTRODUCTION AND OBJECTIVES: Increasing numbers of small renal cell carcinomas (RCC) are being incidentally detected and followed longitudinally without surgical intervention. As additional cases of RCC’s are identified, we need to ensure that methods of detecting these individuals in regional cancer registries (CR) are timely and reflect clinical practice. The objective of this study was to identify if a gap exists in kidney cancer surveillance infrastructure which leads to a systematic underestimation of the true incidence of kidney cancer as reported by CR’s. METHODS: In Phase I of our study, data from 638 patients with a physician billing code for kidney cancer in 2008 (ICD-9: 189.0) was linked to the provincial CR. Individual patient chart review was performed to confirm diagnosis on discrepant cases. In Phase II of our study, a prospectively maintained database of 95 patients on active surveillance with presumed RCC in 2012 was linked with the CR. These years were chosen to allow for lag time of CR data capture. Data linkage statistics between these two sources and CR data are presented. RESULTS: Phase I revealed 184 patients (29%) with administratively coded kidney cancer were not captured in the CR. Ninety-five of these patients (52%) were not found for two reasons: no final cancer diagnosis was determined as per the current CR inclusion criteria or patients resided out of province. The remaining 89 patients (48%) were previously registered but with a nonkidney cancer. Phase II showed that 19 patients (20%) were identified in the CR with RCC. Of the remaining 76, 48 patients (50%) were eligible to be entered into the registry data as determined by CR rules. The remaining 28 patients (30%) did not meet current CR inclusion criteria. Thus we confirmed our hypothesized gap between CR reported and the true incidence of kidney cancer in both phases of our study. CONCLUSIONS: When utilizing administrative data, we identified a large proportion of patients with presumed kidney cancer who were not captured in the CR. When the system is challenged further by comparing it with a prospectively collected surveillance series with a lower rate of histological diagnosis, the gap is much greater. Traditionally, CR’s have relied heavily on histological confirmation for identification of patients as gold-standard cases of kidney cancer. This work demonstrates the need for CR’s to identify appropriate alternative sources of diagnostic data for non-histologically confirmed cancers. This will allow for the accurate quantification of the true incidence and burden of kidney cancer.