Comorbidities amongst Indigenous cancer patients: impact on treatment and survival
METHODS: Adult Indigenous cancer patients diagnosed at a public hospital during 1998-2004 in the state of Queensland were identified via the cancer registry. Comorbidities at diagnosis were obtained from medical records. A modified Charlson Comorbidity Index (CCI), a measure of both severity and number of comorbidities, was calculated and categorised into a 3-point scale: no score (zero), 1, and 2+. Logistic regression was used to calculate the odds (OR) of treatment uptake, and Cox Proportional Hazard regression were used to calculate the relative risk of death (HR) of those with (CCI≥1) and without comorbidities (CCI=0).
RESULTS: Amongst Indigenous cancer patients, 481 (50%) had no CCI score, 256 (27%) a score of 1, and 219 (23%) a score of 2+. The most common comorbidities were diabetes (n=287, 30%), cardiovascular (n=222, 23%), and respiratory disease (n=134, 14%). Older patients had higher levels of comorbidities (p<0.001), and those with the greatest comorbidity burden (CCI=2+) were more likely to be diagnosed with advanced stage cancer than those with less (CCI = 1) or no comorbidities (CCI=0) (p=0.006). Those with comorbidities compared to those without were less likely to have received cancer treatment (OR=0.48, 95%CI 0.35-0.64), and less likely to have survived (any-cause survival: HR=1.65, 95%CI 1.41-1.94; cancer-specific survival: HR=1.63, 95%CI 1.371.94); even when adjusting for cancer type, age, stage of disease and treatment uptake (any-cause survival: HR=1.38, 95%CI 1.15-1.66; cancer-specific survival: HR=1.39, 95%CI 1.14-1.69).
CONCLUSIONS: Indigenous cancer patients typically manage multiple, and perhaps competing, comorbid conditions which may lead to reduced cancer treatment and poorer survival.