The Diagnostic Interval of Colorectal Cancer Patients in Ontario by Degree of Rurality
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Background: Wait times while moving through the cancer diagnostic process are a public health concern. Rural populations may experience more challenges in accessing cancer care, which could translate into a longer diagnostic interval and represent a healthcare inequity. This project analyzed the association between rurality of residence and the diagnostic interval of colorectal cancer (CRC) patients in Ontario, Canada. Methods: This was a retrospective population-based cohort study. We used administrative databases available through the Institute for Clinical Evaluative Sciences (ICES) to identify incident CRC cases diagnosed from Jan 1, 2007- May 31, 2012. We assigned each patient a rurality score, based on their census subdivision, and calculated the length of their diagnostic interval. We defined the diagnostic interval as the time (in days) between a patient’s first diagnostic-related encounter with the health care system to the CRC diagnosis date. Data linkage through ICES allowed us to describe variations in cancer stage and the diagnostic interval by degree of rurality of patient residence and to analyze associations through multivariable models taking into account potential confounders. Results: Overall, the median diagnostic interval of the CRC cohort was 64 (IQR: 22-159) days and the 90th percentile was 288 days. Patients with stage I CRC had a longer median diagnostic interval than patients with stage IV CRC. Across rurality categories, a significant difference in median diagnostic interval was detected in the stage I stratum only, ranging from 58.5 to 108 days (p=0.0005), but with the most rural group having the shortest diagnostic interval. Results from adjusted multivariable models suggested that patients in mid-ranged rural categories had similar or longer diagnostic intervals compared to patients in the least rural category while patients in the most rural category maintained the shortest diagnostic intervals. Important covariates included age, comorbidities and CRC sub-site. Conclusion: Our results do not support a rurality effect on stage or the diagnostic interval in the hypothesized direction. Estimates of a shorter interval in the most rural category, especially for stage I disease, call for a deeper analysis to better understand care delivery in those areas and patient characteristics that might affect the interval.