Background: Identification of prognostic factors in patients with cancer of unknown primary (CUP) is important to optimize their management.
Aim: To study the clinicopathological characteristics of patients with CUP and to identify factors that influence their survival.
Methods: A retrospective review of the medical records of 102 patients who presented with CUP in two Egyptian cancer care facilities during six years from 2012 to 2017 inclusive.
Results: The median age of patients was 61 years (range: 40-96) and 63% were males. Well-/moderately-differentiated adenocarcinoma was the most common histopathological diagnosis (60%) followed by poorly-differentiated carcinoma (25%). The common sites of metastases were the liver (56%), lymph nodes (56%), lungs (44%), and bones (38%). The initial treatment plan was single modality treatment in 43% of patients, combined modality in 16%, and best supportive care in 41%. The 6-month time-to-progression (TTP) and overall survival (OS) rates were 52.7% and 56.1%, respectively.  Eastern Cooperative Oncology Group (ECOG) performance status >1, bone metastasis, low serum albumin, elevated serum alkaline phosphatase, and single agent chemotherapy treatment (compared to combination chemotherapy) were associated with significantly shorter TTP. Age ≥65 years, ECOG performance status >1, comorbidities, >1 metastatic site, bone metastasis, low serum albumin, elevated serum alkaline phosphatase, best supportive care / single modality treatment plan and single agent chemotherapy treatment (compared to combination chemotherapy) were associated with significantly shorter OS.
Conclusions: Many factors may affect the prognosis of CUP patients, e.g., old age, poor performance status, and low serum albumin. Further studies including a larger sample size are needed to develop predictive models based on these factors in patients with CUP.