Clinicopathological associations of p16 expression, high-risk HPV genotypes, and tumor-infiltrating lymphocytes on prognosis in anal squamous cell carcinoma.

e15503 Background: Anal squamous cell carcinoma (ASCC) is a rare malignancy with an increasing incidence worldwide. Chronic infection with high-risk human papillomavirus (HR-HPV) is a main etiologic factor. Viral oncoproteins E6 and E7 disrupt cell-cycle regulation, leading to p16 overexpression. Tumour-infiltrating lymphocytes (TILs) is a promising biomarker in solid tumors. Methods: We conducted a retrospective analysis of patients with ASCC treated with definitive chemoradiotherapy (CRT). We collected clinical and pathological data. Nuclear (N-p16) and cytoplasmatic p16 (C-p16) expression and TILs were assessed by immunohistochemistry and hematoxylin and eosin–stained sections. HR-HPV status was determined using a PCR-based commercial assay. Survival was analyzed using Kaplan–Meier and Cox models. Results: 86 patients (pts) were included; median age: 57 years (IQR, 47–66), 60% were female, and 88% had ECOG performance status 0–1. Poorly differentiated tumors were observed in 31%, nodal involvement in 69%, and stage III–IV disease in 78% (stage IV due to inguinal nodal involvement). Most patients received CRT (88%), achieving an objective response in 76%. HPV was positive in 90% of evaluable cases, with high-risk genotypes detected in 54%. High N-p16 and C-p16 expression ( > 70%) was observed in 53% and 47%, respectively. Stromal TILs (s-TILs) (73 pts), with a median of 10% (IQR, 5–30); 49% had high s-TILs ( > 10%). After a median follow-up of 58.1 months, median event-free survival (EFS) was 50.4 months (95% CI, 18.6–82.3), while median overall survival (OS) was not reached. In multivariable Cox regression, stage III–IV disease (HR 6.58, 95% CI 1.52–28.44; p = 0.012) and N-p16 low expression (HR 2.50, 95% CI 1.20–5.00; p = 0.013) remained independently associated with inferior EFS. Complete response (CR) after CRT was associated with improved OS (HR 6.64, 95% CI 2.00–21.00; p = 0.001). High N-p16 expression was significantly associated with complete response after CRT (OR = 4.71; 95% CI 1.43–18.68; p = 0.015). Conclusions: In addition to clinical stage p16 expression is a key prognostic biomarker associated with event-free survival and may be useful for risk stratification in patients with ASCC treated with chemoradiotherapy. Characteristic N = 86 1 AgeMedian (Q1–Q3) 57.00 (47.00–66.00) GenderFemale 52(60%) Clinical Stage (AJCC 7 th ed)Stage I–IIStage III-IV 19 (22%)67 (78%) HPV statusPositiveNegativeUnknown 74 (90%)8 (9.8%)4 Nuclear p16 expression High (>70%)Low (<=70%)Unknown 37(53%)33(47%)16 Stromal TILs (sTILs)Median(Q1–Q3) (n=73) 10.00 (5.00–30.00) Response after treatment Partial or completeStable or Progression 65(76%)21(24%) Events (progression or death)Progression or deathDeathCensored 43 (50%)15 (17%)43(50%) Outcomes (median, months)EFSOSFollow-up 50.4Not-reached.58.1