Radiation Records in the National Cancer Database: Variations in Coding and/or Practice Can Significantly Alter Survival Results

Abstract

PURPOSE The aim of the current work was to quantify internally inconsistent and anomalous radiation therapy (RT) data in the National Cancer Database (NCDB) and determine their association with overall survival (OS) using node-positive uterine cancer as a test clinical scenario. MATERIALS AND METHODS We identified all NCDB participants with International Federation of Gynecology and Obstetrics stage IIIC1 to IIIC2 uterine cancer treated with hysterectomy and adjuvant RT between 1998 and 2012. Variables that were reviewed to identify anomalous data included RT site, modality, dose, fractions, timing, duration, and stage. We used χ2 testing to associate anomalous data with reporting facility and demographic variables. OS was estimated using the Kaplan-Meier method and comparison between cohorts was performed using the log-rank test. Univariable and multivariable Cox proportional hazards regression analyses were performed. RESULTS Of the 14,298 analyzed participants, 2,288 (16.0%) had one or more anomalous data entry, 538 (3.8%) likely because of an incomplete RT course. χ2 testing suggested differences in anomalous data prevalence by reporting facility type ( P = .0007), geographic region ( P < .001), distance from participants’ homes ( P < .001), diagnosis year ( P < .001), and location of RT relative to reporting facility ( P = .0038). Five-year OS in those with one or more anomalous data entry was 51.3% versus 58.0% for those without anomalous data ( P < .001), and anomalous data remained significantly associated with OS on multivariable analysis. After excluding insufficient, excessive, or unknown total RT dose, anomalous data were no longer significant on multivariable analysis. CONCLUSION The overwhelming majority of RT data within the NCDB seem to be appropriate for the clinical scenario. Nevertheless, approximately one eighth of participants in this test clinical scenario had adjuvant RT data that were internally inconsistent or outside generously defined norms. The presence of anomalous RT data was significantly associated with compromised OS, an effect not observed after correcting for total RT dose.