Comorbidity and survival of Danish lung cancer patients from 2000–2011: a population-based cohort study

OBJECTIVE To examine lung cancer survival and the impact of comorbidity in the Central Denmark Region from 2000 to 2011. METHODS We performed a population-based cohort study of lung cancer patients diagnosed during four 3-year calendar periods (2000-2002, 2003-2005, 2006-2008, and 2009-2011) in the Central Denmark Region. The Danish National Registry of Patients was used to identify 9,369 incident lung cancer patients, and to obtain data on their Charlson comorbidity index score, categorized as no (score = 0), medium (score = 1-2), or high (score ≥3) level comorbidity. We calculated 1- and 5-year survival in different calendar time periods overall, and by age, sex, and level of comorbidity, and used Cox regression to compute mortality rate ratios (MRR) for each level of comorbidity versus no comorbidity in different calendar time periods. RESULTS Overall 1-year survival increased from 31% in 2000-2002 to 37% in 2009-2011, while the 5-year survival increased from 10% in 2000-2002 to predicted 13% in 2009-2011 with the largest improvement observed for women and patients less than 80 years. The adjusted 1-year MRR in patients with high comorbidity compared with those without comorbidity was 1.23 (95% confidence interval [CI]: 1.05-1.46) in 2000-2002 and 1.35 (95% CI: 1.17-1.56) in 2009-2011. The corresponding adjusted 5-year MRRs were 1.21 (95% CI: 1.04-1.40) in 2000-2002 and 1.26 (95% CI: 1.11-1.42) in 2009-2011. CONCLUSION Lung cancer patients' survival increased from 2000 to 2011 in the Central Denmark Region, most prominently for women under 80 years and patients with no, or medium level of comorbidity. Their prognosis remained nonetheless dismal with overall 5-year survival of 13%, and comorbidity remained a negative prognostic factor.