Health service utilisation and investigations before diagnosis of cancer of unknown primary (CUP): A population-based nested case-control study in Australian Government Department of Veterans' Affairs clients

Population-based data on the use of health services and diagnostic investigations for patients with cancer of unknown primary (CUP) is scarce. It is uncertain whether the pathways to diagnosis are different for CUP compared to other cancers. Methods: We performed a population-based nested matched case-control study using linked routinely collected records for Australian Government Department of Veterans' Affairs clients, 2004-2007. We compared health care consultations, hospitalisations, emergency department visits, and diagnostic procedures in the three months prior and the month of diagnosis for 281 clients registered with a diagnosis of CUP (C809) and 1102 controls randomly selected from clients registered with a first diagnosis of metastatic cancer of known primary. Results: Overall, the median age at cancer diagnosis was 83 years. CUP patients were slightly older and had significantly more comorbidities prior to diagnosis than those with known primary. Compared to known primary, a diagnosis of CUP was significantly more likely after an emergency department visit, less specialist input, fewer invasive diagnostic procedures such as resection or endoscopy, and more non-invasive procedures such as magnetic resonance imaging. There were no differences in primary care or allied health consultations and hospitalisations. Conclusions: This health care pathway suggests delayed recognition of cancer and scope for improvement in the medical management of high-risk individuals presenting to primary care. The pattern of diagnostic investigations reveals under-investigation in some CUP patients but this is likely to reflect recognition of limited treatment options and poor prognosis and is consistent with clinical guidelines.