This study is a single-center, retrospective, observational cohort investigation conducted at Tianjin Cancer Hospital that aims to evaluate the relationship between tumor microenvironment (TME) composition and the efficacy of antibody-based antitumor therapies-including monoclonal antibodies, antibody-drug conjugates, and bispecific antibodies-across a pan-cancer population comprising adult patients with breast, colorectal, head and neck squamous, lung, bladder, gastric, or pancreatic cancer treated between January 2020 and January 2026. Using real-world data extracted from electronic medical records, pathology archives, and laboratory systems, the study will analyze TME-related variables derived from tissue immunohistochemistry, molecular testing, and peripheral blood inflammatory markers in relation to clinical outcomes, with a primary endpoint of either progression-free survival or objective response rate to be finalized before database lock, and secondary endpoints including overall survival, disease control rate, and subgroup heterogeneity across cancer types and drug classes. Statistical analyses will employ Kaplan-Meier survival curves, Cox proportional hazards models, logistic regression, and appropriate multivariable adjustments with sensitivity analyses using propensity score methods, while the study will adhere to ethical standards under a waiver of informed consent due to its minimal-risk, retrospective design and strict de-identification of patient data.

Inclusion Criteria:

• Age 18 years or older
• Pathologically confirmed diagnosis of breast cancer, colorectal cancer, head and neck squamous cell carcinoma, lung cancer, bladder cancer, gastric cancer, or pancreatic cancer
• Received antibody-based antitumor therapy at this center, including monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, or other antibody-based agents, either as monotherapy or combination therapy
• Completed at least one post-treatment efficacy assessment or had evaluable radiographic or clinical documentation of treatment response
• Available key clinical information, including demographics, tumor stage, line of therapy, treatment details, efficacy outcomes, or follow-up data
• Available data for at least one tumor microenvironment-related indicator, including tissue immunohistochemistry, molecular testing, or peripheral blood inflammatory markers

Exclusion Criteria:

• Missing key outcome information, including unevaluable treatment response or absence of follow-up or survival outcome records
• Missing key exposure information, including antibody-based therapy drug name or timing/line of therapy
• Concurrent active malignancy for which treatment outcomes cannot be clearly attributed to the cancer of interest
• Severely incomplete or unverifiable medical records
• Received only supportive or palliative care without exposure to antibody-based antitumor therapy

This retrospective cohort study includes adult patients (≥18 years) with pathologically confirmed breast, colorectal, head and neck squamous, lung, bladder, gastric, or pancreatic cancer who received at least one line of antibody-based antitumor therapy-including monoclonal antibodies, antibody-drug conjugates (ADCs), and bispecific antibodies-at Tianjin Cancer Hospital between January 2020 and January 2026. Eligible patients must have completed at least one cycle of efficacy evaluation with available radiologic or clinical response records, possess complete key clinical data (demographics, staging, treatment details, and follow-up outcomes), and have at least one tumor microenvironment (TME)-related assessment available from tissue immunohistochemistry, molecular testing, or peripheral blood inflammatory markers. Patients are excluded if they lack critical efficacy or exposure data, have a concurrent active malignancy with indistinguishable outcome attribution, present with severely i