Ruth Cunningham

Survival disparities in Indigenous and non-Indigenous New Zealanders with colon cancer: the role of patient comorbidity, treatment and health service factors

Background Ethnic disparities in cancer survival have been documented in many populations and cancer types. The causes of these inequalities are not well understood but may include disease and patient characteristics, treatment differences and health service factors. Survival was compared in a cohort of Maori (Indigenous) and non-Maori New Zealanders with colon cancer, and the contribution of demographics, disease characteristics, patient comorbidity, treatment and healthcare factors to survival disparities was assessed. Methods Maori patients diagnosed as having colon cancer between 1996 and 2003 were identified from the New Zealand Cancer Registry and compared with a randomly selected sample of non-Maori patients. Clinical and outcome data were obtained from medical records, pathology reports and the national mortality database. Cancer-specific survival was examined using Kaplan–Meier survival curves and Cox hazards modelling with multivariable adjustment. Results 301 Maori and 328 non-Maori patients with colon cancer were compared. Maori had a significantly poorer cancer survival than non-Maori (hazard ratio (HR)=1.33, 95% CI 1.03 to 1.71) that was not explained by demographic or disease characteristics. The most important factors contributing to poorer survival in Maori were patient comorbidity and markers of healthcare access, each of which accounted for around a third of the survival disparity. The final model accounted for almost all the survival disparity between Maori and non-Maori patients (HR=1.07, 95% CI 0.77 to 1.47). Conclusion Higher patient comorbidity and poorer access and quality of cancer care are both important explanations for worse survival in Maori compared with non-Maori New Zealanders with colon cancer.

Social inequalities or inequities in cancer incidence? Repeated census-cancer cohort studies, New Zealand 1981–1986 to 2001–2004

BackgroundWe examine incidence trends for 18 adult cancers, by ethnicity and socioeconomic position in New Zealand.MethodsThe 1981 to 2001 censuses were linked to subsequent cancer registrations, giving 47.5 million person-years of follow-up.ResultsEthnicity: Pooled over time, differences were marked: Pacific and Māori rates of cervical, endometrial, stomach and pancreatic cancers were 1.5–2.5 times European/Other rates; Māori, Pacific and Asian rates of liver cancer were 5 times European/Other; European/Other rates of colorectal, bladder and brain cancers were 1.5–2 times the rates of other groups and melanoma rates 5–10 times higher; Pacific and Asian kidney cancer rates were half those of Māori and European/Other.Over time, Māori and Pacific rates of cervical cancer fell faster and Māori rates of colorectal and breast cancer increased faster, than European/Other rates. Male lung cancer rates decreased for European/Other, were stable for Māori and increased for Pacific. Female lung cancer rates increased for all ethnic groups.Income: Other than lung (rate ratio 1.35 men, 1.56 women), cervical (1.35) and stomach cancer (1.23), differences in incidence by income were modest or absent.ConclusionsTobacco explains many of the social group trends and differences and constitutes an inequity. Cervical cancer trends are plausibly explained by screening and sexual practices. Faster increases of colorectal and breast cancer among Māori are presumably due to changes in dietary and reproductive behaviour, but the higher Māori breast cancer rate is unexplained.Ethnic differences in bladder, brain, endometrial and kidney cancer cannot be fully explained.

Ethnic and socioeconomic trends in breast cancer incidence in New Zealand

BackgroundBreast cancer incidence varies between social groups, but differences have not been thoroughly examined in New Zealand. The objectives of this study are to determine whether trends in breast cancer incidence varied by ethnicity and socioeconomic position between 1981 and 2004 in New Zealand, and to assess possible risk factor explanations.MethodsFive cohorts of the entire New Zealand population for 1981-86, 1986-1991, 1991-1996, 1996-2001, and 2001-2004 were created, and probabilistically linked to cancer registry records, allowing direct determination of ethnic and socioeconomic trends in breast cancer incidence.ResultsBreast cancer rates increased across all ethnic and socioeconomic groups between 1981 and 2004. Māori women consistently had the highest age standardised rates, and the difference between Māori and European/Other women increased from 7% in 1981-6 to 24% in 2001-4. Pacific and Asian women had consistently lower rates of breast cancer than European/Other women over the time period studied (12% and 28% lower respectively when pooled over time), although young Pacific women had slightly higher incidence rates than young European/other women. A gradient between high and low income women was evident, with high income women having breast cancer rates approximately 10% higher and this difference did not change significantly over time.ConclusionsDifferences in breast cancer incidence between European and Pacific women and between socioeconomic groups are explicable in terms of known risk factors. However no straightforward explanation for the relatively high incidence amongst Māori is apparent. Further research to explore high Māori breast cancer rates may contribute to reducing the burden of breast cancer amongst Māori women, as well as improving our understanding of the aetiology of breast cancer.

Cancer survival in the context of mental illness: a national cohort study

OBJECTIVE To explore the reasons for worse cancer survival in people with experience of mental illness, including differences by cancer type and psychiatric diagnosis. METHOD New Zealand breast and colorectal cancer registrations (2006-2010) were linked to psychiatric hospitalization records for adults (18-64 years). Cancer-specific survival was compared for recent psychiatric service users and nonusers using Cox regression. The contributions of deprivation, comorbidity and stage at diagnosis were assessed for those with schizophrenia or bipolar affective disorder (Group A) and others using mental health services (Group B). RESULTS Of 8762 and 4022 people with breast and colorectal cancer respectively, 440 (breast) and 190 (colorectal) had recent contact with psychiatric services. After adjusting for confounding, risk of death from breast cancer was increased for Group A [Hazard Ratio (HR) 2.55 (95% confidence interval 1.49-4.35)] and B [HR 1.62 (1.09-2.39)] and from colorectal cancer for Group A [HR 2.92 (1.75-4.87)]. Later stage at diagnosis contributed to survival differences for Group A, and comorbidity contributed for both groups. Fully adjusted HR estimates were breast: Group A 1.65 (0.96-2.84), B 1.41 (0.95-2.09); colorectal: Group A 1.89 (1.12-3.17), B 1.25 (0.89-1.75)]. CONCLUSIONS The high burden of physical disease and delayed cancer diagnosis in those with psychotic disorders contributes to worse cancer survival in New Zealand psychiatric service users.

Incidence and management of hepatocellular carcinoma among Māori and non‐Māori New Zealanders

Objective: To investigate time trends in hepatocellular carcinoma (HCC) incidence disparities, and ethnic differences in risk factors, comorbidity and treatment pathways among HCC patients.

Measuring cancer in indigenous populations

It is estimated that there are 370 million indigenous peoples in 90 countries globally. Indigenous peoples generally face substantial disadvantage and poorer health status compared with nonindigenous peoples. Population-level cancer surveillance provides data to set priorities, inform policies, and monitor progress over time. Measuring the cancer burden of vulnerable subpopulations, particularly indigenous peoples, is problematic. There are a number of practical and methodological issues potentially resulting in substantial underestimation of cancer incidence and mortality rates, and biased survival rates, among indigenous peoples. This, in turn, may result in a deprioritization of cancer-related programs and policies among these populations. This commentary describes key issues relating to cancer surveillance among indigenous populations including 1) suboptimal identification of indigenous populations, 2) numerator-denominator bias, 3) problems with data linkage in survival analysis, and 4) statistical analytic considerations. We suggest solutions that can be implemented to strengthen the visibility of indigenous peoples around the world. These include acknowledgment of the central importance of full engagement of indigenous peoples with all data-related processes, encouraging the use of indigenous identifiers in national and regional data sets and mitigation and/or careful assessment of biases inherent in cancer surveillance methods for indigenous peoples.

Like Minds, Like Mine: Seventeen Years of Countering Stigma and Discrimination Against People with Experience of Mental Distress in New Zealand

In 1996 New Zealand was one of the first countries in the world to initiate a comprehensive national programme to combat stigma and discrimination against people with experience of mental illness. Combining national level social marketing and community-driven education and training with a range of other strategies, the programme became known as Like Minds, Like Mine and achieved international recognition as the ‘gold standard’ in stigma reduction initiatives. Serial evaluations have demonstrated success in shifting public attitudes, and there are indications that discriminatory behaviours are also reducing. A great deal has been learnt about the extent of social exclusion and discrimination experienced by New Zealanders living with mental illness and about effective strategies to change attitudes and counter discrimination. Seventeen years later the work of Like Minds, Like Mine to increase social inclusion and reduce discrimination continues. This chapter documents the origins, evolution and current status of the Like Minds, Like Mine programme (referred to as Like Minds).

Impact of Comorbidity on Cancer Screening and Diagnosis

The presence of coexistent chronic disease or comorbid illness has been shown to have an impact on the pathogenesis of cancer and on the frequency of screening, the stage at diagnosis, the intensity of treatment, and, therefore, on cancer outcomes. This chapter will focus on how comorbid illness affects cancer screening and diagnosis. There is some disagreement in the literature regarding how the comorbidity burden affects the screening and stage of cancer, particularly when specific comorbidities and the overall burden of comorbidity, measured by some aggregate index, are examined. Moreover, the extent of the relationship between comorbidity and cancer may be affected by the method by which the comorbidity burden is measured, with regard to breadth (number of comorbidities) and depth (severity of comorbidities). We consider some of these factors in this chapter as we examine the literature in view of four hypotheses: (1) The surveillance hypothesis, which suggests that patients with comorbid illnesses are screened more regularly or are more likely to be diagnosed earlier because they have more frequent contact with the medical care system. (2) The competing demand hypothesis, which posits that patients with comorbidities are screened less or diagnosed later because other chronic conditions represent a competing demand upon physician time and focus. (3) The physiological hypothesis, which argues that comorbid illness actually affects the pathogenesis, progression, and/or severity of cancer. (4) The death from other causes hypothesis, which suggests that patients or their physicians choose not to screen, because of the risk of death from a cause of other than cancer.