Racial disparities in cancer-related survival in patients with squamous cell carcinoma of the esophagus in the US between 1973 and 2013

Abstract

Background: Esophageal cancer makes up approximately 1% of all diagnosed cancers in the US. There is a persistent disparity in incidence and cancer-related mortality rates among different races for esophageal squamous cell carcinoma (SCC). Most previous studies investigated racial disparities between black and white patients, occasionally examining disparities for Hispanic patients. Studies including Asians/Pacific Islanders (API) as a subgroup are rare. Our objective was to determine whether there is an association between race and cancer-related survival in patients with esophageal SCC.

Methods and findings: This was a retrospective cohort study using the National Cancer Institute's Surveillance, Epidemiology, and End Result (SEER) database. The SEER registry is a national database that collects information on all incident cancer cases in 13 states of the United States and covers nearly 26% of the US population Patients aged 18 and over of White, Black, or Asian/Pacific Islander (API) race with diagnosed esophageal SCC from 1973 to 2013 were included (n = 13,857). To examine overall survival, Kaplan-Meier curves were estimated for each race and the log-rank test was used to compare survival distributions. Cox proportional hazards models were used to estimate unadjusted and adjusted hazard ratios with 95% confidence intervals. The final adjusted model controlled for sex, marital status, age at diagnosis, decade of diagnosis, ethnicity, stage at diagnosis, and form of treatment. Additional analyses stratified by decade of diagnosis were conducted to explore possible changes in survival disparities over time. After adjustment for potential confounders, black patients had a statistically significantly higher hazard ratio compared to white patients (HR 1.08; 95% confidence interval (CI) 1.03-1.13). However, API patients did not show a statistically significant difference in survival compared with white patients (HR 1.00; 95% CI 0.93-1.07). Patients diagnosed between 1973 and 1979 had twice the hazard of death compared to those diagnosed between 2000 and 2013 (HR 2.05, 95% CI 1.93-2.19). Patients diagnosed in 1980-1989 and 1990-1999 had had HRs of 1.59 (95% CI 1.51-1.68) and 1.33 (95% CI 1.26-1.41), respectively. After stratification according to decade of diagnosis, the HR for black patients compared with white patients was 1.14 (95% CI 1.02-1.29) in 1973-1979 and 1.12 (95% CI 1.03-1.23) in 1980-1989. These disparities were not observed after 1990; the HR for black patients compared with white patients was 1.03 (95% CI 0.93-1.13) in 1990-1999 and 1.05 (95% CI 0.96-1.15) in 2000-2013.

Conclusions: Black patients with esophageal SCC were found to have a higher hazard of death compared to white and API patients. Survival disparities between races appear to have decreased over time. Future research that takes insurance status and other social determinants of health into account should be conducted to further explore possible disparities by race.

Fig 1. Adjusted survival curves, by race, for adult patients in the SEER database diagnosed with esophageal squamous cell carcinoma, 1973–2013.

Fig 2. Adjusted survival curves, by race, for adult patients in the SEER database diagnosed with esophageal squamous cell carcinoma, 1970–1979.

Fig 3. Adjusted survival curves, by race, for adult patients in the SEER database diagnosed with esophageal squamous cell carcinoma, 1980–1989.

Fig 4. Adjusted survival curves, by race, for adult patients in the SEER database diagnosed with esophageal squamous cell carcinoma, 1990–1999.

Fig 5. Adjusted survival curves, by race, for adult patients in the SEER database diagnosed with esophageal squamous cell carcinoma, 2000–2013.