Comorbidity and early death in Danish stage I lung cancer patients - an individualised approach

Background: Comorbidity is an important prognostic marker and a treatment indicator for lung cancer patients. Register-based studies often describe the burden of comorbidity by the Charlson comorbidity index (CCI) based on hospital discharge data. We assessed the association between somatic and psychiatric comorbidity and death within one year in early lung cancer and, furthermore, the burden of comorbidity according to treatment type.Material and methods: We conducted a population-based matched case-control study of stage I lung cancer identifying all treated patients who died (all-cause) within one year after diagnosis (early death group, cases). On the basis of data from the Danish Lung Cancer Registry these patients were then matched with two controls who survived more than one year (survivors). Through a review of the medical records, we validated inclusion criteria and collected data on somatic and psychiatric comorbidity. We assessed the association between comorbidity and early death with multivariate conditional logistic regression.Results: We included 221 cases and 410 controls. The mean CCI score in the early death group was 2.3 vs. 1.3 in the survivor group (p < .001). Still, 22% vs. 30% had a CCI score of zero (p = .04) with an average number of comorbidities among these patients of 1.63 vs. 1.06 respectively (p = .006). Among women, 23% in the early death group had depression vs. 13% in the survivor group, corresponding to an unadjusted odds ratio (OR) of 2.0 (CI 95% 1.0-3.7). However, in an adjusted analysis (incl. somatic comorbidities) the OR was 1.7 (CI 95% 0.8-3.5). Patients undergoing oncological therapy were older and tended to have more somatic comorbidities than the surgically treated patients.Conclusion: Comorbidity remains a significant prognostic marker even for stage I lung cancer patients with a CCI score of zero. The suggested association between early death and depression among women needs to be studied further.