Evaluation of the prognostic benefit of identifying the probable primary site in cancer of unknown primary

With the development of site-specific cancer therapy, identifying the primary origin allows the oncologist to personalise therapy for patients with the cancer of unknown primaries (CUPs). At present, immunohistochemistry (IHC) screening is the standard method used to postulate the primary site in CUP. In this retrospective study, we evaluated the prognostic benefit of identifying the primary site in CUP. All 84 patients who presented with suspected CUP to the Royal Stoke University Hospital between 2011 and 2012 were included in our study. Forty-eight percent (40/84) of these patients were unable to undergo necessary investigations to identify primary sites because of poor performance status. IHC screening was able to postulate the primary site in 59% (26/44) of the remaining patients with confirmed CUP. Therefore, the primary site was not identified in a significant proportion of patients with CUP. The median survival of confirmed CUP with probable primary site was 2.0 months (95% confidence interval (CI): 1.2 to 2.9 months), whereas the median survival of confirmed CUP with no probable primary site was 4.1 months (95% CI: 1.5 to 9.7 months). This difference in survival time was statistically significant. In addition, using the Cox regression model, we found that patients with confirmed CUP with primary sites had prognostically unfavourable diseases with a shorter median survival, regardless of the age of disease onset, gender, sites of metastases or number of metastases. One approach to improve the survival would be to start systemic therapy at the earliest possible opportunity rather than waiting for all investigation results, such as IHC.