Background: Older patients are notably absent from clinical trials. Thus, observational studies are the primary avenue for understanding the role of comorbidity in cancer care and survival. We examined the impact of comorbidity on systemic treatment initiation and 3-year survival in a cohort of older cancer patients.
Patients and methods: Our cohort comprised 2753 Australian veterans aged ≥65 years with full health coverage and a cancer registry notification for colorectal (CRC), breast, prostate or non-small-cell lung cancer (NSCLC). We established comorbidities based on drugs prescribed in the 6 months prior to cancer diagnosis.
Results: Patients with higher comorbidity burden were more likely to receive systemic treatment for prostate cancer [adjusted odds ratio 1.21, 95% confidence interval (CI) 1.05-1.39] but less likely for NSCLC (0.63, 95% CI 0.45-0.86). After adjusting for receipt of treatment, increased comorbidity resulted in shorter survival for CRC [adjusted hazard ratio (aHR) 1.16, 95% CI 1.07-1.26] and breast cancer (aHR 1.23, 95% CI 1.02-1.48). However, we did not demonstrate significant improvements in 3-year survival for patients receiving systemic treatment.
Conclusion: Comorbidity influences systemic treatment uptake and adversely affects survival, with impact dependent upon comorbidity and cancer type. Clinical trials should be undertaken in older patients to better understand the risks and benefits of cancer treatments.