Survival Outcome in True Carcinoma of Unknown Primary (tCUP) with p16 + Cervical Metastasis.

Introduction  Age and lymph node ratio have been attributed as independent predictors for survival and recurrence in carcinoma of unknown primary (CUP). Objective  The purpose of this study was to analyze the prognostic value of p16 overexpression for CUP in the absence of true primary (TP). Methods  The study involved 43 patients who underwent therapeutic lymph node dissection (LND) from 2000 to 2015 after all the diagnostic work up for CUP. Immunohistochemistry for p16 overexpression was performed. Cox proportional hazard regression analysis was used to analyze the prognostic impact on 5-year overall survival (OS) and recurrence-free survival (RFS). Results  The male-to-female ratio was 5.1:1, with a median age of 62 years. The clinicopathological data, except for p16 overexpression, did not differ significantly in terms of 5-year OS and RFS. The Cox regression analysis proposed p16 positivity to be an independent prognosticator of regional recurrence-free survival (RRFS) (hazard ratio [HR] 6.180, p  = 0.21). The median time to recurrence and death were 10 and 25 months, respectively. Conclusion  Cervical metastasis with p16 overexpression is a significant prognostic factor of improved RFS after surgery in CUP. The prognostic significance of lymph node p16 positivity should be further studied.