# Impact of Small Area Level Deprivation on Colorectal Cancer Survival: Findings from the Regional Cancer Registry in Korea

## TL;DR

This study finds that socioeconomic deprivation in local areas is linked to lower survival rates for colorectal cancer, especially in advanced cases and over time.

## Contribution

The study introduces new evidence on how small-area deprivation impacts colorectal cancer survival, emphasizing disparities in deprived regions.

## Key findings

- Each unit increase in deprivation index correlates with a 6.6% decrease in survival probability.
- Deprived areas show steeper survival probability declines for distant-stage colorectal cancer over time.
- Regional deprivation has a stronger impact on long-term survival than short-term outcomes.

## Abstract

This study examines the impact of socioeconomic deprivation at the small-area level on colorectal cancer (CRC) survival. By analyzing data from 34,999 CRC patients in the Busan Regional Cancer Registry, we explored survival disparities linked to individual and regional factors. Our findings indicate that greater deprivation correlates with lower survival probabilities, particularly among patients with advanced-stage disease and over longer periods. This research highlights the importance of addressing socioeconomic inequalities in health policy and cancer care and advocates for targeted measures to improve treatment accessibility in deprived areas. The insights gained can inform health equity initiatives and resource allocation to enhance CRC survival outcomes.

Background/Objectives: Research on the relationship between small-area-level deprivation and cancer survival, particularly for colorectal cancer (CRC), is lacking. Therefore, we investigated the relationship among small area-level deprivation, individual-level factors, and CRC survival using data from the Busan Regional Cancer Registry. Methods: We analyzed 34,999 patients with CRC from the Busan Regional Cancer Registry from 2003 to 2020. The primary outcome was CRC mortality. The explanatory variables at the individual level included age, gender, cancer stage, and year of diagnosis, whereas the Deprivation Index (DI) was used at the regional level. We conducted a multilevel survival analysis with frailty to assess the impact of individual- and area-level factors on survival probabilities. Results: In the multilevel survival model, each unit increase in the DI at the area level was associated with a 6.6% decrease in survival probability. When applying Model 2 and deriving regional estimates using the empirical Bayesian estimation method, the graph of the DI (x-axis) against survival probability (y-axis) showed that the slope of the regional DI for the 3-year and 5-year survival probabilities increased compared with the 1-year rate across all stages of the disease. Additionally, the slopes were steeper for the distant stage than for the local or regional stages. Conclusions: Small-area level deprivation negatively affects CRC survival, especially in distant-stage patients and those with longer disease duration.