Health Service Use, Treatment Patterns, and Survival for Cancer of Unknown Primary: A Data Linkage Study (#133)
Background: Cancer of unknown primary origin (CUP) is a diagnosis used for patients with metastatic cancer and no identified primary site. CUP is the 9th most frequently diagnosed cancer and 7th most common cause of cancer death in NSW. We know little about health service use and treatment patterns of CUP patients, nor how these measures compare for patients with metastatic cancer with a known primary site.
Methods: Australian Government Department of Veterans’ Affairs clients with incident CUP (n=285) were identified using the NSW Central Cancer Registry and matched on month and year of diagnosis with incident metastatic cancer cases of known primary (n=1,082). Health service use was ascertained using linked hospitalisation, dispensing, and health services data. Receipt of cancer treatment (surgery, chemotherapy, radiotherapy) was compared using conditional logistic regression, accounting for differences in follow-up time; survival was compared using stratified Cox regression. Factors associated with treatment and survival among CUP cases were also identified.
Results: The median age at diagnosis was similar for patients with CUP and known primary (84 vs. 83 years); 65% of both groups were male. Compared to patients with metastatic cancer of known primary, patients with CUP: were less likely to receive cancer treatment (OR 0.29, 95%CI 0.19–0.44); were more likely to die within one month (HR 3.83, 95%CI 2.06–7.13) and up to two years after diagnosis (HR 1.53, 95%CI 1.18–1.98); and had 43% fewer GP, specialist and allied health visits and 20% fewer hospitalisations in the year after diagnosis. CUP patients diagnosed on the basis of pathology rather than clinically were more likely to receive treatment (OR 2.25, 95%CI 0.90–5.67).
Conclusion: At presentation, patients diagnosed with CUP may have more advanced metastatic disease or more aggressive disease; these factors may affect survival and the decision to treat.