Predictive Biomarkers for PD-1 Inhibitor Response in Squamous Cell Carcinoma

This multicenter retrospective-prospective cohort study evaluates predictive biomarker and tissue-pathology features for response to PD-1 inhibitor-based therapy in patients with squamous cell carcinoma (SCC). Model inputs include blood ELISA, tissue multiplex immunofluorescence (mIF), PD-L1 assessment, pretreatment biopsy/H\&E-based pathology features, and baseline clinicopathological variables, assessed individually or in combination. The retrospective component will analyze clinical data and pretreatment tissue and blood specimens from SCC patients treated with PD-1 inhibitor-based therapy from May 2020 onward across participating centers. These data will be used to develop and refine a predictive model or risk-score framework and to evaluate associations with objective response rate (ORR), pathological response where applicable, duration of response (DoR), progression-free survival (PFS), event-free survival (EFS), and overall survival (OS). The prospective component begins in September 2025 and will enroll up to 800 participants. Eligible patients may receive PD-1 inhibitor therapy with or without chemotherapy, including disease-specific cohorts receiving neoadjuvant anti-PD-1 therapy plus chemotherapy where applicable. Baseline clinical data and pretreatment samples will be collected before treatment initiation. Tumor tissue, biopsy or H\&E slides obtained within 6 months where available, and blood samples collected within 28 days where available will be used for biomarker and tissue-pathology analyses. Patients will be followed at baseline and at weeks 4, 8, and 12 where applicable, with quarterly survival follow-up. Response may be assessed using RECIST 1.1 and/or pathological response criteria, including tumor regression grade where applicable; for neoadjuvant patients, postoperative tumor regression grade and treatment failure before surgery may be incorporated according to a prespecified response-assessment rule. Within the prospective component, the ESCC-specific cohort includes consecutive treatment-naive patients receiving neoadjuvant anti-PD-1 blockade plus chemotherapy and supports locked-model evaluation using pretreatment endoscopic biopsy H\&E slides.

Inclusion Criteria: 1. Patients with pathologically confirmed esophageal squamous cell carcinoma (ESCC), head and neck squamous cell carcinoma (HNSCC), cervical squamous cell carcinoma (CSCC), or lung squamous cell carcinoma (LSCC), regardless of surgical eligibility 2. For surgically eligible patients: Planned to receive neoadjuvant PD-1 inhibitor ± chemotherapy as first-line treatment 3. For surgically ineligible patients: Planned to receive PD-1 inhibitor ± chemotherapy as first-line treatment 4. Availability of pre-treatment biopsy tissue and baseline blood samples 5. Capable of providing informed consent Exclusion Criteria: 1. Patients with concurrent other types of malignancies 2. Patients who have already undergone prior antitumor therapy