Income differences in time to colon cancer diagnosis

Abstract

Introduction: People with low income have worse outcomes throughout the cancer care continuum; however, little is known about income and the diagnostic interval. We described diagnostic pathways by neighborhood income and investigated the association between income and the diagnostic interval.

Methods: This was a retrospective cohort study of colon cancer patients diagnosed 2007-2019 in Ontario using routinely collected data. The diagnostic interval was defined as the number of days from the first colon cancer encounter to diagnosis. Asymptomatic pathways were defined as first encounter with a colonoscopy or guaiac fecal occult blood test not occurring in the emergency department and were examined separately from symptomatic pathways. Quantile regression was used to determine the association between neighborhood income quintile and the conditional 50th and 90th percentile diagnostic interval controlling for age, sex, rural residence, and year of diagnosis.

Results: A total of 64,303 colon cancer patients were included. Patients residing in the lowest income neighborhoods were more likely to be diagnosed through symptomatic pathways and in the emergency department. Living in low-income neighborhoods was associated with longer 50th and 90th-percentile symptomatic diagnostic intervals compared to patients living in the highest income neighborhoods. For example, the 90th percentile diagnostic interval was 15 days (95% CI 6-23) longer in patients living in the lowest income neighborhoods compared to the highest.

Conclusion: These findings reveal income inequities during the diagnostic phase of colon cancer. Future work should determine pathways to reducing inequalities along the diagnostic interval and evaluate screening and diagnostic assessment programs from an equity perspective.

Keywords: colon cancer; diagnostic delay; diagnostic interval; diagnostic pathways; income; inequalities; inequities; neoplasms.

FIGURE 1

Cohort exclusions.

FIGURE 2

Frequency of diagnostic pathways by income quintile. (Neighborhood income quintile 1 = lowest; neighborhood income quintile 5 = highest).

FIGURE 3

Median and interquartile range diagnostic interval for diagnostic pathway by income quintile (Dots on the far right represent the 90th percentile, dots within the lines represent the 50th percentile, with the end of the left side being the 25th percentile and the end of the right side the 75th percentile).