A population-based examination of cancer in New South Wales farm residents compared to rural non-farm and urban residents

Abstract

The cancer indicators and outcomes of rural Australians are generally less favourable than those of their urban counterparts, but the situation for farm residents is less well known. With a focus on farm residents, this study aimed to identify differences between farm, rural non-farm and urban residents in a large NSW cohort, in: (1) incidence and mortality from major cancers; (2) screening rates, stage at diagnosis and selected cancer therapies; and (3) common risk factors associated with these cancers. Cancers of interest were breast, cervical, colorectal, lung and prostate cancers; melanoma and Non Hodgkins Lymphoma. The Sax Institute’s 45 and Up Study was used to define resident groups and to compare baseline cancer-related risk factors. Cancer mortality, incidence, stage at diagnoses, cancer screening practices and selected cancer treatments were compared through data linkage with routine state and national health datasets. Direct age-standardisation, proportional hazards regression and logistic regression were used to compare cancer indicators, controlling for common risk factors. Overall, farm residents had lower all cancer incidence and mortality risk than rural non-farm or urban counterparts, but differences were only significant for all cancer incidence in farm women compared to rural non-farm women. For specific cancers, breast cancer mortality risk was also significantly lower in farm women than rural non-farm women, but incidence and mortality risk for other cancers were not significantly different. However, whilst confidence intervals did not exclude unity, adjusted point estimates for incidence or mortality risk suggest that compared to other groups, farm residents had a similar or reduced risk of breast, colorectal and lung cancer; similar risk of NHL; and farm men similar or slightly raised risk of melanoma and prostate cancer. There were no significant differences in stage at diagnosis for prostate, breast and colorectal cancers. Small case numbers in the farm group were likely to have contributed to lack of significance of findings for some analyses. Screening practices of farm and rural non-farm residents were generally similar; but both rural groups had significantly less frequent PSA tests, Pap tests, mammograms and colonoscopies than urban residents. Cancer-related surgical services for breast and colorectal cancer were comparable between all groups. Some findings for non-surgical therapies should be considered with caution, but both farm and rural non-farm residents were significantly less likely to access chemotherapy for breast cancer and brachytherapy for prostate cancer than urban counterparts. Strengths and limitations of the research are discussed. Pending confirmation of findings in other studies, results have implications for cancer screening and treatment services in rural Australia. The reasons why farm residents may have lower incidence and / or mortality risk for some cancers should also be considered for further research.