A study of head and neck cancer treatment and survival among indigenous and non-indigenous people in Queensland, Australia, 1998 to 2004

Overall, Indigenous Australians with cancer are diagnosed with more advanced disease, receive less cancer treatment and have poorer cancer survival than non-Indigenous Australians [1, 2]. However, the prognosis for Indigenous people with specific cancers such as those of the head and neck is largely unknown.

The term "cancers of the head and neck" refers to a group of cancers that occur on the lip, tongue, gum, oral cavity, the sinuses, nose, salivary glands and throat [3]. Most head and neck tumours are squamous cell carcinomas (SCC) for which significant risk factors include smoking and alcohol exposure, and increasingly, infection by human papillomavirus (HPV), which now reportedly accounts for 25% of cases in the United States [4]. Head and neck cancers rank as the fifth most commonly occurring cancer type for Australia overall [5] and also for Indigenous people in Queensland [6].

Little is known about the incidence and mortality of head and neck cancer among Indigenous relative to non-Indigenous populations in the developed world. Overall incidence of oral and pharyngeal cancers amongst American Indians/Alaskan Natives (AI/AN) was reportedly lower than for whites but varied widely across districts of the United States, and stage distribution was found to be less favourable for AI/AN [7]. In the Indigenous population of the Northern Territory of Australia, the incidence of head and neck cancer is around 32.78 per 100,000 compared to 19.5 per 100,000 for the rest of Australia [8] and higher incidence and mortality from cancer of the oropharynx have previously been reported in the Northern Territory Indigenous population when compared to non-Indigenous people [2]. Whilst incidence was reportedly similar among Indigenous and non-Indigenous people with head and neck cancers in Queensland between 1997 and 2006, mortality was more than three times greater for Indigenous people [6].

It is not known to what extent established prognostic factors such as late stage at diagnosis, the presence and severity of comorbidities or differences in cancer treatment account for the excess mortality among Indigenous Australians with head and neck cancer. Therefore we conducted this population-based study to compare these factors and survival between Indigenous and non-Indigenous Australians diagnosed with this disease.

This study reports clinical characteristics, treatment and survival for 67 Indigenous people diagnosed with head and neck cancer between 1998 and 2004 in Queensland, Australia. As the number of cases was small, and the data collection restricted to information available from medical records, the study is largely descriptive in nature and limited in interpretive power. As a result of matching, Indigenous and non-Indigenous people with head and neck cancer in this study shared a similar demographic profile for location of residence, age and sex, and all attended Queensland public hospitals. We found that only 7% of Indigenous and 11% of non-Indigenous patients were diagnosed with metastatic disease, in keeping with reports that advanced stage at diagnosis is relatively uncommon for head and neck cancer [14].

Overall, Indigenous people with head and neck cancer were less likely to receive any cancer treatment and when only cases with non-metastatic disease were compared, the treatment disparity was even greater. How this compares with other Indigenous populations with head and neck cancer is not known as no similar published data are available. However, treatment bias among Indigenous people with cancer in general, and with other specific cancers, has been reported in a number of studies [1, 15–17]. The reasons why Indigenous people in this study were less likely to receive treatment are not precisely known but we found that those Indigenous people who do not receive treatment were likely to be older, male and socially disadvantaged compared to non-Indigenous people who did not receive treatment. Indigenous people were also less likely to receive curative treatment than their non-Indigenous counterparts.

A number of barriers to the use of cancer and other health services for Indigenous Australians have been identified in the literature, and include lack of proximity, availability and cultural appropriateness of health services, lack of specialist care, transport, health insurance and health services affordability, as well as inadequate proficiency in English [16, 18–20]. In general these details were not available from the medical records, and are therefore not assessed in this study. Reports suggest factors such as late stage at diagnosis [17], greater prevalence of comorbidities [1] and disparate treatment decisions made by health professionals based on assumptions about socioeconomic and cultural factors [21] may explain some of the treatment differential, but reports are not conclusive.

There was no significant difference in cancer stage or comorbidities between Indigenous and non-Indigenous patients in the present study that might account for the treatment differential, and although we are confident that the medical records were a reliable source of information on cancer stage and the most important comorbidities such as those included in the Charlson index (e.g. diabetes, cardiovascular disease), we acknowledge that our study was small and consequently had limited power to detect small differences between the groups with certainty; consequently some differences may not have been detected. However, it is well known that there is a greater overall burden of comorbidities among the Australian Indigenous population in general and in those with cancer [1, 15] and given that Indigenous head and neck cancer patients in this study were 7 times more likely to die from causes other than cancer than non-Indigenous patients, and around 6 times more likely to die from other causes after accounting for any cancer treatment received, it is plausible that chronic ill-health is associated with less treatment.

We acknowledge some possible under-representation of Indigenous patients in this study due to misclassification of Indigenous status at the QCR; however a data quality audit of Queensland hospitals, who provide cancer notification to the QCR, suggest a high level of accurate identification, so this is likely to be minimal [22]. We also believe the Indigenous to non-Indigenous comparison to be internally valid, with little, if any, misclassification of Indigenous status in the study sample, as medical charts were carefully reviewed to verify Indigenous status and discrepant cases were excluded. Unfortunately smoking history was not routinely available from the medical records for this study and we were therefore unable to investigate possible associations between smoking and head and neck cancer for this population. As up to 40% of Indigenous people are reported to smoke and smoking has been strongly associated with head and neck cancer [23], we recommend more thorough collection of smoking data in the health records of Indigenous patients to enable better assessment of the long-term impact on the health of this population.

Indigenous people who did receive treatment were significantly less likely to receive surgery with adjuvant radiotherapy, the most commonly administered mode of treatment for head and neck cancer in the early stages [4]. However, as mode of treatment varies depending on the tumour site and extent and, as the distribution of cancer types differed somewhat among Indigenous and non-Indigenous people in the present study, it was difficult to compare treatment modes between the two groups. When those who had treatment were compared, there was no difference in dose, duration or completion rate of radiotherapy between Indigenous and non-Indigenous people with head and neck cancer and overall, time to any treatment and curative treatment was also similar. Although numbers were small, the implication is that once engaged in treatment, the treatment pathway was likely to be similar between Indigenous and non-Indigenous people in the public setting in Queensland. This accords with a 2006 report by Condon and colleagues who found that whilst Indigenous patients were less likely to be recommended treatment, there was no significant difference in completion [15].

When cancer-specific death was adjusted for socioeconomic status, the presence and severity of comorbidities and cancer stage, the survival difference remained the same and changed little when adjusted for treatment. However, when curative treatment and mode of treatment were taken into account, the survival difference was no longer significant. This might suggest that if the same treatment was offered, Indigenous people would have similar survival from head and neck cancer as non-Indigenous people. Although the numbers in our cohort were small and so the results lacked statistical precision, we identified disparities in cancer treatment delivery which should be further investigated and addressed by health service personnel. Although survival from head and neck cancer in Indigenous populations has not been reported elsewhere, the results of this study are consistent with the poor cancer survival and worse mortality that has been extensively reported for Indigenous people in Australian with other cancers [24, 25]. We were unable to adjust for the presence of HPV which has been found to be a predictor of survival in whites in America [26] as HPV testing was not routinely undertaken at the time of the study.

Despite the small sample size, the study obtained statistically significant and clinically important differences in treatment and survival in Indigenous people with head and neck cancer in Queensland Australia. Indigenous people treated in the public health system in Queensland were similar in socioeconomic status and stage of disease to non-Indigenous people and received less treatment and had poorer survival than non-Indigenous people with head and neck cancer. Further study is needed to ascertain to what extent the observed differences may be explained by differences in the true burden of comorbidities in Indigenous and non-Indigenous people.