The effects of comorbidity on colorectal cancer mortality in an Australian cancer population

Maleshwane Lettie Pule,Elizabeth Buckley,David Roder,Theophile Niyonsenga

doi:10.1038/s41598-019-44969-8

Maleshwane Lettie Pule, Elizabeth Buckley + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-44969-8

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Journal: Scientific Reports	Publication Date: Jun 12, 2019
Citations: 26	License type: open-access

Affiliation: University of South Australia

Abstract

This study estimated the absolute risk of colorectal cancer (CRC) specific and other-cause mortality using data from the population-based South Australian Cancer Registry. The impact of competing risks on the absolute and relative risks of mortality in cases with and without comorbidity was also investigated. The study included 7115 staged, primary CRC cases diagnosed between 2003 and 2012 with at least one year of follow-up. Comorbidities were classified according to Charlson, Elixhauser and C3 comorbidity indices, using hospital inpatient diagnoses occurring five years before CRC diagnosis. To estimate the differences in measures of association, the subdistribution hazard ratios (sHR) for the effect of comorbidity on mortality from the Fine and Gray model were compared to the cause-specific hazards (HR) from Cox regression model. CRC was most commonly diagnosed in people aged ≧ 70 years. In cases without comorbidity, the 10-year cumulative probability of CRC and other cause mortality were 37.1% and 17.2% respectively. In cases with Charlson comorbidity scores ≥2, the 10-year cumulative probability of CRC-specific and other cause mortality was 45.5% and 32.2%, respectively. Comorbidity was associated with increased CRC-specific and other cause mortality and the effect differed only marginally based on comorbidity index used.

Highlights

Colorectal cancer (CRC) is a major cause of mortality and morbidity worldwide, accounting for an estimated 694 000 deaths in 20121
We investigated whether the association between comorbidity and the risk of mortality depends on how comorbidity is derived, using two commonly used generic comorbidity indices and a cancer-specific comorbidity index
This study explored the impact of comorbidity on colorectal cancer (CRC) and other cause mortality in an Australian population after adjusting for known associations of stage, grade, sociodemographic characteristics and calendar year of diagnosis

Summary

Introduction

Colorectal cancer (CRC) is a major cause of mortality and morbidity worldwide, accounting for an estimated 694 000 deaths in 20121. 5-year relative CRC survival increased in Australia from 50% to 69% between 1984–1988 and 2009–20132, CRC still contributes significantly to mortality, accounting for about 9% of all cancer deaths[2]. A population-based study in New South Wales indicated a decreased survival with increasing age, greater disease spread and higher Charlson comorbidity index (CCI) score[4]. Few studies have compared the predictive performance of these generic indices against cancer-specific ones to assess their comparative performance in adjusting for comorbid conditions when comparing cancer mortality risk in cancer populations. In studies that have included comorbidity measures, a lower survival has generally been found with increasing comorbidity[12,13] The reasons for this trend have not been clear, possible contributors include under-treatment and reduced resilience to cope with cancer effects and treatment toxicity. It is possible that comorbidity could vary across populations and that the best comorbidity index would vary with the populations under study and would need to be customized for maximum effect

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