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BackgroundComorbidity has a well documented detrimental effect on cancer survival. However it is difficult to disentangle the direct effects of comorbidity on survival from indirect effects via the influence of comorbidity on treatment choice. This study aimed to assess the impact of comorbidity on colon cancer patient survival, the effect of comorbidity on treatment choices for these patients, and the impact of this on survival among those with comorbidity.MethodsThis retrospective cohort study reviewed 589 New Zealanders diagnosed with colon cancer in 1996–2003, followed until the end of 2005. Clinical and outcome data were obtained from clinical records and the national mortality database. Cox proportional hazards and logistic regression models were used to assess the impact of comorbidity on cancer specific and all-cause survival, the effect of comorbidity on chemotherapy recommendations for stage III patients, and the impact of this on survival among those with comorbidity.ResultsAfter adjusting for age, sex, ethnicity, area deprivation, smoking, stage, grade and site of disease, higher Charlson comorbidity score was associated with poorer all-cause survival (HR = 2.63 95%CI:1.82–3.81 for Charlson score ≥ 3 compared with 0). Comorbidity count and several individual conditions were significantly related to poorer all-cause survival. A similar, but less marked effect was seen for cancer specific survival. Among patients with stage III colon cancer, those with a Charlson score ≥ 3 compared with 0 were less likely to be offered chemotherapy (19% compared with 84%) despite such therapy being associated with around a 60% reduction in excess mortality for both all-cause and cancer specific survival in these patients.ConclusionComorbidity impacts on colon cancer survival thorough both physiological burden of disease and its impact on treatment choices. Some patients with comorbidity may forego chemotherapy unnecessarily, increasing avoidable cancer mortality.

A case-control study has previously been reported of asthma deaths in people aged 5-45 years who had a hospital admission for asthma (the index admission) in New Zealand during 1981-1987. The study has been re-analysed to examine the association between markers of asthma severity and risk of asthma death or hospital admission; patients prescribed fenoterol were excluded from this re-analysis because of the previously reported interaction between fenoterol, asthma severity, and asthma deaths. The re-analysis included 39 patients who died of asthma during the 12 months after their index admission, 226 patients who had a readmission for asthma during the 12 months after their index admission, and 263 controls chosen from all index admissions. An admission in the previous 12 months was the strongest marker of subsequent risk of death (odds ratio (OR) = 3.5, 95% confidence interval (CI): 1.8-6.9, P less than 0.01), and was also a strong marker of subsequent risk of readmission (OR = 3.0, 95% CI: 2.1-4.2, P less than 0.01); the risk increased with the number of previous admissions. Three or more categories of prescribed asthma drugs was also associated with subsequent death (OR = 1.7, 95% CI: 0.9-3.3, P = 0.13) or readmission (OR = 1.9, 95% CI: 1.3-2.7, P less than 0.01); prescribed oral corticosteroids was only weakly associated with subsequent death (OR = 1.3, 95% CI: 0.6-2.8, P = 0.59), but was more strongly associated with subsequent readmission (OR = 1.9, 95% CI: 1.2-2.8, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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