Higher Comorbidity Burden does not Explain Lower Survival for Indigenous Australian Women with Cervical Cancer

Background: We aimed to investigate the effect of comorbidity on cervical cancer survival for Australian women, and whether it contributed to the excess mortality of Indigenous Australian women compared to non‐Indigenous women.

Method: Cervical cancer cases diagnosed 2003–2012 in six Australian states/territories (covering 96% of the Australian female population) were linked to hospital inpatient records for the identification of comorbidity data. The weighted Charlson comorbidity index was calculated and categorised as a score 0 (no comorbidity), 1 or 2+. Kaplan Meier 5‐year cause‐specific survival probabilities were calculated by Indigenous status and comorbidity level. Flexible parametric survival models were used to model excess mortality by comorbidity score, for Indigenous and non‐Indigenous women. The effect of comorbidity on cancer stage at diagnosis was also investigated for a sub‐group of women from NSW, for whom staging data was available.

Results: 4,467 Australian women (4.4% Indigenous) with cervical cancer were included. Indigenous women were younger and had more comorbidity at diagnosis (score ≥1 24% vs. 10%, respectively). Indigenous women had lower survival than non‐Indigenous women (60% vs. 77%). After adjustment for study factors, increased comorbidity was clearly associated with increased mortality for non‐Indigenous women, but not for Indigenous women. Stratified analysis showed that the survival disparity between Indigenous women and non‐Indigenous women was contained to those without comorbidity (HR 2.5, 95%CI 1.9‐3.4). Indigenous and non‐Indigenous women with comorbidity had similar survival.

Conclusion: The difference in survival for Indigenous and non‐Indigenous women without comorbidity warrants further investigation and may reflect differences in how health services engage these women.