Time dependent ethnic convergence in colorectal cancer survival in Hawaii

Abstract

Background: Although colorectal cancer death rates have been declining, this trend is not consistent across all ethnic groups. Biological, environmental, behavioral and socioeconomic explanations exist, but the reason for this discrepancy remains inconclusive. We examined the hypothesis that improved cancer screening across all ethnic groups will reduce ethnic differences in colorectal cancer survival.

Methods: Through the Hawaii Tumor Registry 16,424 patients diagnosed with colorectal cancer were identified during the years 1960-2000. Cox regression analyses were performed for each of three cohorts stratified by ethnicity (Caucasian, Japanese, Hawaiian, Filipino, and Chinese). The models included stage of diagnosis, year of diagnosis, age, and sex as predictors of survival.

Results: Mortality rates improved significantly for all ethnic groups. Moreover, with the exception of Hawaiians, rates for all ethnic groups converged over time. Persistently lower survival for Hawaiians appeared linked with more cancer treatment.

Conclusion: Ethnic disparities in colorectal cancer mortality rates appear primarily the result of differential utilization of health care. If modern screening procedures can be provided equally to all ethnic groups, ethnic outcome differences can be virtually eliminated.

Figure 1

Estimated Survival versus Time (Years) by Ethnicity. Estimated survival (survivor functions) versus time (years) stratified by ethnicity for each cohort (1960–1974, 1975–1987, and 1988–2000) and cause of death category, controlling for the effects of SEER stage at diagnosis, year of diagnosis, age, and sex are provided.

Figure 2

Estimated Survival versus Time (Years) by Ethnicity. Estimated survival (survivor functions) versus survival time (years) stratified by ethnicity for the third cohort (1988–2000) controlling for the effects of SEER stage at diagnosis, year of diagnosis, age, sex, and treatment are provided.