There are no population-based data on the whole-of-system health care prior to CUP diagnosis.
To compare the pre-diagnosis use of health services and diagnostic investigations for patients with CUP and metastatic malignancy of known primary.
Population-based nested matched case-control study using linked routinely collected health records for Australian Government Department of Veterans’ Affairs (DVA) clients, 2004-2007. 281 DVA clients registered with a diagnosis of CUP (C809) and 1102 controls randomly selected from clients registered with a diagnosis of metastatic malignancy of known primary. Controls were matched by month/year of diagnosis, health care entitlement, and follow-up prior to diagnosis. Consultations/visits and diagnostic procedures in the three months prior and the month of diagnosis were analysed using logistic regression adjusting for socio-demographic characteristics and comorbid conditions.
There were no differences in GP or allied health consultations and hospitalisations, but CUP patients were less likely to have a specialist consultation (odds ratio 0.50, 95% confidence interval 0.33-0.76), and more likely to have an emergency department visit (1.60, 1.18-2.17). CUP patients were less likely to have non-surgical resection (0.65, 0.48-0.87), surgical resection (0.40, 0.28-0.58), exploratory surgery (0.21, 0.08-0.60), or endoscopy (0.31, 0.22-0.44), and more likely to have a CT scan (2.16, 1.47-3.19), ultrasound (1.82, 1.33-2.49), and MRI (3.02, 1.61-5.68). Cytology (1.60, 1.10-2.32) and immunohistochemistry (2.51, 1.60-3.93) were more common and histopathology less common (0.41, 0.27-0.63) for CUP patients.
Compared to known primary, CUP is more likely after an emergency department visit, less specialist input, and fewer invasive diagnostic procedures. This pathway might suggest delayed recognition of cancer and thus scope for improvement in the medical management of high-risk individuals presenting to GPs. There is under-investigation in some CUP patients but this may reflect recognition of limited treatment options and poor prognosis and is consistent with clinical guidelines for CUP.