Objectives Comorbidity influences survival in ovarian cancer, but the causal relations between prognosis and comorbidity are not well characterized. The aim of this study was to investigate the associations between comorbidity, system delay, the choice of primary treatment, and survival in Danish ovarian cancer patients.

Methods This population-based study was conducted on data from 5317 ovarian cancer patients registered in the Danish Gynecological Cancer Database. Comorbidity was classified according to the Charlson Comorbidity Index and the Ovarian Cancer Comorbidity Index. Pearson χ² test and multivariate logistic regression analyses were used to investigate the association between comorbidity and primary outcome measures: primary treatment (“primary debulking surgery” vs “no primary surgery”) and system delay (more vs less than required by the National Cancer Patient Pathways [NCPPs]). Cox regression analyses, including hypothesized mediators stepwise, were used to investigate if the impact of comorbidity on overall survival is mediated by the choice of treatment or system delay.

Results A total of 3945 patients (74.2%) underwent primary debulking surgery, whereas 1160 (21.8%) received neoadjuvant chemotherapy. When adjusting for confounders, comorbidity was not significantly associated to the choice of treatment. Surgically treated patients with moderate/severe comorbidity were more often experiencing system delay longer than required by the NCPP. No association between comorbidity and system delay was observed for patients treated with neoadjuvant chemotherapy. Survival analyses demonstrated that system delay longer than NCPP requirement positively impacts survival (hazard ratio, 0.90 [95% confidence interval, 0.82–0.98]), whereas primary treatment modality has no significant impact on survival.

Conclusions Patients with moderate/severe comorbidity experience often a longer system delay than patients with no or mild comorbidity. Age, stage, and comorbidity are factors influencing the choice of treatment, with stage being the most important factor and comorbidity of lesser importance. The impact of comorbidity on survival does not seem to be mediated by the choice of treatment or system delay.