Cancer diagnosis, treatment, and survival in Indigenous and non-Indigenous Australians: a matched cohort study

Abstract

Background: Indigenous Australians do not have the high standard of health that Australians in general have, and have worse outcomes for several diseases such as cancer. However, few comparative data exist to prove this disparity. We assessed differences in disease stage at cancer diagnosis, treatment, and survival between these two populations in Queensland.

Methods: Indigenous people diagnosed with cancer between 1997 and 2002 were identified through the cancer registry and compared with randomly selected non-Indigenous patients who were frequency-matched for age, sex, place of residence, cancer site, and year of diagnosis. We obtained details of treatment from hospital medical records. We restricted analyses to patients treated in the public sector, since less than 5% of Indigenous cases were treated privately. We used multivariate models, mainly Cox regression analyses, to assess differences.

Findings: We studied 815 Indigenous and 810 non-Indigenous cancer patients. Stage at diagnosis differed significantly (p=0.007): 47% of Indigenous versus 53% of non-Indigenous patients had localised cancer, 22% versus 21% had distant metastases, and 12% versus 7% had no information on stage in the medical chart examined. Comorbidities such as diabetes mellitus or chronic renal disease were more common in Indigenous patients. These individuals were less likely to have had treatment for cancer (surgery, chemotherapy, radiotherapy), and waited longer for surgery (hazard ratio=0.84, 95% CI 0.72-0.97) than non-Indigenous patients. After adjustment for stage at diagnosis, treatment, and comorbidities, non-Indigenous patients had better survival than Indigenous ones (hazard ratio=1.3, 95% CI 1.1-1.5).

Interpretation: Non-Indigenous cancer patients survive longer than Indigenous ones, even after adjustment for stage at diagnosis, cancer treatment, and greater comorbidity in Indigenous cases. We believe that better understanding of cultural differences in attitudes to cancer and its treatment could translate into meaningful public-health and clinical interventions to improve cancer survival in Indigenous Australians.