P53 And P16 Expression Profiles Reveal Three Prognostically Relevant Subgroups In Vulvar Cancer: A Tma Based Study By The Ago-Care-Translational Study Group.

5592 Background: Currently, there are two major pathways for tumorigenesis of vulvar squamous cell carcinoma (VSCC) – an HPV-dependent with p16 overexpression as a surrogate for HPV-associated transformation and an HPV-independent route linked to lichen sclerosus, characterized by p53 mutation. A possible correlation of HPV dependency with a favourable prognosis has been proposed. Methods: The AGO CaRE-1 study is a retrospective survey of pts with primary VSCC FIGO stage ≥1B (UICC-TNM version 6) treated at 29 gynecologic cancer centers in Germany 1998-2008 (n = 1,618). For this CaRE-translational sub-study available FFPE tissue was collected centrally (n = 648). A tissue micro array (TMA) was constructed; p16 and p53 expression was determined by immunohistochemistry (IHC). HPV status and subtype were analyzed by PCR. Results: p16 IHC was interpretable in 550 TMA spots and considered positive in 166/550 (30.2%). HPV DNA was detected in 78.4% of the p16+ tumors, with HPV 16 being the most common subtype (88.3%) . Pts with p16+ tumors were younger at diagnosis (63 vs. 70 yrs for p16- tumors; p = 0 < 0.01) and showed lower rates of lymph-node involvement (29.0% vs. 39.7%; p = 0.021). p53 IHC was interpretable in 597 spots, 187/597 (31.3%) were considered positive. Pts with p53+ tumors were older at first diagnosis (71 vs. 66 yrs; p = 0.001 for p53- tumors) and showed lymph-node involvement more often (43.3% vs. 31.1%; p = 0.007). There was a relevant number of tumors with neither p16 nor p53 overexpression (221/535); while co-expression of p53 and p16 was rare (12/535). For survival analyses, three groups were defined: p53+ (n = 163), p16+/p53- (n = 151) and p16-/p53- (n = 221). 2-y-disease-free (DFS) and overall survival (OS) rates were significantly different between the groups: DFS: p53+ 47.0%; p16-/p53- 53% and p16+/p53- 65.5% (p < 0.001); OS: 70.4%, 72.6% and 82.7% (p = 0.003), respectively. Adjustment for age and nodal status showed consistent p16 and p53 effects regarding DFS. Conclusions: p16 overexpression is associated with an improved prognosis in VSCC while p53 positivity is linked to an adverse outcome. Our data provide evidence of a clinically relevant third subgroup of VSCC with a p53-/p16- phenotype showing an intermediate prognosis that needs to be further characterized.