HPV Infection and Immunohistochemical Analysis of P16, P53, and PD-L1 Expression as Prognostic Biomarkers in Squamous Cell Anal Cancer Patients Receiving Definitive Radiotherapy/Chemoradiotherapy

PURPOSE/OBJECTIVE(S)

The treatment of anal squamous cell carcinoma (SCC) with definitive radiotherapy (RT)/chemoradiotherapy (CRT) has a high likelihood of success; nevertheless, treatment resistance and recurrence rates cannot be ignored. Therefore, we aimed to identify the relationship between immunohistochemical (IHC) evaluation, treatment response, and prognosis.

MATERIALS/METHODS

This retrospective study included 42 patients with anal SCC treated with definitive RT/CRT at a single institution between 2006 and 2020. Detection of high-risk HPV-DNA and IHC analysis of p16, p53, and PD-L1 expression was performed from diagnostic formalin-fixed, paraffin-embedded (FFPE) biopsies. Positive staining was accepted as >5% in tumor cells for p16 and p53 expression in addition to ≥1% combined positive score (CPS) [(PD-L1 positive tumor, lymphocyte, macrophage count/total viable cell count) x100] for PD-L1 expression.

RESULTS

Thirty patients (71.4%) had a complete response to definitive RT/CRT. Recurrence was observed in 16 (38.1%) patients, with 3 (7.1%) having locoregional recurrence (LRR), 6 (14.3%) having distant metastases (DM), and 7 (16.7%) having both LRR and DM. Twenty-four (57.1%) patients were alive. Thirty (71.4%) patients were HPV+, while 12 (28.6%) were HPV-. There was a significant correlation between HPV+ and p16+ status (p<0.001). HPV- status was associated with the male gender (p = 0.001). HPV- and p16- status were significantly associated with a lack of complete response to definitive RT/CRT (p<0.001, p<0.001, respectively). Furthermore, there was a significant relationship between lack of complete response and increased recurrence (p = 0.016) and distant metastases (p = 0.015). Ten of the 16 patients with recurrence were p53+; a significant correlation was found between recurrence and p53+ status (p = 0.006). Similarly, p53+ status was associated with increased LRR (p = 0.014). PD-L1 CPS ≥ 1% was found in 31 (73.8%) patients. PD-L1 positivity was significantly correlated with HPV+ (p = 0.026) and p16+ (p = 0.013) status. All 10 (23.8%) patients with LRR were PD-L1+; PD-L1 CPS ≥ 1% was associated with poor local control (p = 0.031). In univariate analysis, age [<65] (p = 0.049), complete response (p = 0.015), and HPV+ status (p = 0.010) were related to increased 5-year (y) overall survival (OS); complete response (p = 0.001), HPV+ status (p = 0.025) and p53- status (p = 0.010) were associated with increased 5-y disease-free survival (DFS). In multivariate analysis, age [<65] (p = 0.010) and HPV+ status (p = 0.002) were significant prognostic factors for 5-y OS, whereas complete response (p = 0.007) and p53- status (p = 0.038) were significant prognostic factors for 5-y DFS.

CONCLUSION

Patients with HPV- status and/or poor prognostic biomarkers should be identified at diagnosis. Thus, better outcomes can be achieved with different treatment options, such as combining immunotherapy and standard CRT.