Aims

CUP is one of the ten most common cancers and the fourth most common cause of cancer death worldwide. We describe the recent trends in diagnosis and survival of CUP, focusing on socio-economic disparities.

Methods

We performed a Surveillance, Epidemiology and End Results (SEER) based analysis of subjects with CUP diagnosed in the US 1973 - 2008. Demographic and tumour characteristics were correlated with outcomes.

Results

The proportion of cancer cases diagnosed as CUP has decreased consistently over time, more than halving since 1973 (2.3% vs 1.5% in 1973 and 2008 respectively, p<0.001). Of 106,641 CUP patients identified, only 78% had pathologic confirmation. This did not change considerably from the 1970’s to the 2000’s, (76.5% vs 77.1%, respectively). However, a pathologic diagnosis was more common in areas of higher affluence and higher education (79% vs 74%, p<0.001). A higher proportion of CUP was diagnosed in females, blacks and residents of less affluent or less educated counties throughout most of the study period. The median survival of CUP was 3 months, with only a marginal improvement over time (3 vs 4 months for those diagnosed in 1973-79 and 2000-08, respectively). Factors associated with an improved survival on multivariate analysis include: white race; female; <65 years at diagnosis; most recent decade at diagnosis; grade 1 tumour; squamous cell carcinoma (compared to non-squamous); currently married (compared to single ); a histologic diagnosis and treatment by radiotherapy (all p<0.001). Despite the improvement in survival with radiotherapy, the use of radiotherapy was less frequent in females and blacks.

Conclusion

The prognosis of CUP patients is poor but highly dependent on histological type. Pleasingly the proportion of cancers diagnosed as CUP is decreasing. However, significant disparities in the diagnosis and survival between socioeconomic groups still exist, suggesting inequalities in access to diagnostic investigations and treatment.