Effects of socioeconomic status on esophageal adenocarcinoma stage at diagnosis, receipt of treatment, and survival: A population-based cohort study

Abstract

The incidence of esophageal adenocarcinoma (EAC) is increasing worldwide and has overtaken squamous histology in occurrence. We studied the impact of socioeconomic status (SES) on EAC stage at diagnosis, receipt of treatment, and survival. A population-based retrospective cohort study was conducted using Ontario Cancer Registry-linked administrative health data. Multinomial logistic regression was used to examine the association between SES (income quintile) and stage at EAC diagnosis and EAC treatment. Survival times following EAC diagnosis were estimated using Kaplan-Meier method. Cox proportional-hazards regression analysis was used to examine the association between SES and EAC survival. Between 2003-2012, 2,125 EAC cases were diagnosed. Median survival for the lowest-SES group was 10.9 months compared to 11.6 months for the highest-SES group; the 5-year survival was 9.8% vs. 15.0%. Compared to individuals in the highest-SES group, individuals in the lowest-SES category experienced no significant difference in EAC treatment (91.6% vs. 93.3%, P = 0.314) and deaths (78.9% vs. 75.6%, P = 0.727). After controlling for covariates, no significant associations were found between SES and cancer stage at diagnosis and EAC treatment. Additionally, after controlling for age, gender, urban/rural residence, birth country, health region, aggregated diagnosis groups, cancer stage, treatment, and year of diagnosis, no significant association was found between SES and EAC survival. Moreover, increased mortality risk was observed among those with older age (P = 0.001), advanced-stage of EAC at diagnosis (P < 0.001), and those receiving chemotherapy alone, radiotherapy alone, or surgery plus chemotherapy (P < 0.001). Adjusted proportional-hazards model findings suggest that there is no association between SES and EAC survival. While the unadjusted model suggests reduced survival among individuals in lower income quintiles, this is no longer significant after adjusting for any covariate. Additionally, there is an apparent association between SES and survival when considering only those individuals diagnosed with stage 0-III EAC. These analyses suggest that the observed direct relationship between SES and survival is explained by patient-level factors including receipt of treatment, something that is potentially modifiable.

Fig 1. Kaplan-Meier survival estimates of people diagnosed with esophageal adenocarcinoma by socioeconomic status, 120 months follow-up time (log-rank test: P = 0.085).

Income quintile 1, lowest socioeconomic status; Income quintile 5, highest socioeconomic status.

Fig 2

2A-2D. Kaplan-Meier survival estimates of people according to stage at EAC diagnosis by socioeconomic status, 120 months follow-up time. (A) Stage 0-I (log-rank test: P = 0.075); (B) Stage II (log-rank test: P = 0.005); (C) Stage III (log-rank test: P = 0.045); (D) Stage IV (log-rank test: P = 0.045). Income quintile 1, lowest socioeconomic status; Income quintile 5, highest socioeconomic status.

Fig 3

3A-3G. Kaplan-Meier survival estimates of people who received treatment for with esophageal adenocarcinoma by socioeconomic status, 60 months follow-up time. (A) surgery alone (log-rank test: P = 0.798); (B) chemotherapy alone (log-rank test: P = 0.662); (C) radiotherapy alone (log-rank test: P = 0.689); (D) surgery + chemotherapy (log-rank test: P = 0.266); (E) surgery + radiotherapy (log-rank test: P = 0.416); (F) chemotherapy + radiotherapy (log-rank test: P = 0.903); and (G) surgery + chemotherapy + radiotherapy (log-rank test: P = 0.243) Income quintile 1, lowest socioeconomic status; Income quintile 5, highest socioeconomic status.