Socioeconomic disparities in colorectal cancer survival: contributions of prognostic factors in a large Australian cohort

PURPOSE: We quantified the contributions of prognostic factors to socioeconomic disparities in colorectal cancer survival in a large Australian cohort. METHODS: The sample comprised 45 and Up Study participants (recruited 2006–2009) who were subsequently diagnosed with colorectal cancer. Both individual (education attained) and neighbourhood socioeconomic measures were used. Questionnaire responses were linked with cancer registrations (to December 2013), records for hospital inpatient stays, emergency department presentations, death information (to December 2015), and Medicare and Pharmaceutical Benefits claims for subsidised procedures and medicines. Proportions of socioeconomic survival differences explained by prognostic factors were quantified using multiple Cox proportional hazards regression. RESULTS: 1720 eligible participants were diagnosed with colorectal cancer after recruitment: 1174 colon and 546 rectal cancers. Significant colon cancer survival differences were only observed for neighbourhood socioeconomic measure (p = 0.033): HR = 1.55; 95% CI 1.09–2.19 for lowest versus highest quartile, and disease-related factors explained 95% of this difference. For rectal cancer, patient- and disease-related factors were the main drivers of neighbourhood survival differences (28–36%), while these factors and treatment-related factors explained 24–41% of individual socioeconomic differences. However, differences remained significant for rectal cancer after adjusting for all these factors. CONCLUSION: In this large contemporary Australian cohort, we identified several drivers of socioeconomic disparities in colorectal cancer survival. Understanding of the role these contributors play remains incomplete, but these findings suggest that improving access to optimal care may significantly reduce these survival disparities.