Immune-Stromal Landscape in Muscle-Invasive Bladder Cancer

The Immune-Stromal Landscape of Muscle-Invasive Urothelial Bladder Carcinoma: A Morphological Histopathological Study

Bladder cancer is a significant global health issue. When the cancer spreads into the muscle layer of the bladder (muscle-invasive bladder cancer), a common treatment is the surgical removal of the bladder (radical cystectomy). However, even after surgery, it can be difficult for doctors to accurately predict how an individual patient's disease will progress using standard staging methods.

This retrospective observational study aims to find better ways to predict patient outcomes by examining the tumor microenvironment, which is the environment immediately surrounding the cancer cells. Specifically, researchers are looking at the relationship between the tumor cells, the surrounding supportive tissue (the stroma), and the patient's natural immune cells.

The study will review existing medical records and archived tumor tissue samples from at least 100 patients who underwent radical cystectomy at the South Egypt Cancer Institute between 2018 and 2024. Under a microscope, researchers will assess three main features:

• Tumor-Stroma Ratio (TSR): The amount of tumor tissue compared to the surrounding supportive tissue.
• Tumor-Infiltrating Lymphocytes (TILs): The number of immune cells that have moved into the tumor to try and fight it.
• Tertiary Lymphoid Structures (TLS): Organized clusters of immune cells that form near the tumor.

By analyzing these features, the researchers hope to determine if specific patterns of immune and supportive cells are linked to better or worse survival rates, such as Overall Survival and Disease-Free Survival. Understanding this immune-stromal landscape could lead to more personalized risk assessments and better treatment plans for future bladder cancer patients.

Urothelial carcinoma is the predominant histological type of bladder cancer, representing about 90% of cases. In Egypt, a substantial shift in histopathological patterns has been observed over recent decades, with urothelial carcinoma emerging as the dominant subtype over squamous cell carcinoma. The clinical outcome of bladder cancer is influenced by established prognostic factors such as tumor stage and histological grade. However, these parameters are frequently unable to fully capture the biological heterogeneity of the disease, limiting their ability to accurately predict individual patient outcomes.

This limitation has prompted interest in identifying additional prognostic markers within the tumor microenvironment. Morphological and immune-related parameters are increasingly recognized as valuable indicators of tumor aggressiveness and epithelial-mesenchymal transition.

To investigate this, histopathological assessment will be performed on the representative slide for each patient featuring the deepest invasion, highest tumor grade, and minimal necrosis. Tumor grade and pathological stage will be determined based on the American Joint Committee on Cancer (AJCC) staging system (8th edition), and histological subtypes will be confirmed according to the 2022 World Health Organization (WHO) classification. Additional parameters to be assessed include coagulative tumor necrosis, surgical margin status, lymph node metastasis, lymphovascular invasion (LVI), and perineural invasion (PNI).

The study will strictly evaluate the following morpho-immune parameters:

• Tumor-Stroma Ratio (TSR): TSR will be assessed at the invasive tumor front using a standardized scoring system. Tumors will be classified into two categories: stroma-high (> 50% stromal component) and stroma-low (≤ 50% stromal component).
• Tumor-Infiltrating Lymphocytes (TILs): The density of TILs will be evaluated on H&E-stained sections using the semi-quantitative Klintrup-Mäkinen (KM) scoring system. The immune response will be categorized into four grades (0-3), which will be further stratified into low-grade (0-1) and high-grade (2-3) immune responses.
• Tertiary Lymphoid Structures (TLS): TLSs will be histologically evaluated focusing on the tumor's invasive edge. The evaluation is based on three quantitative parameters: average density, hotspot density, and maximal diameter.
• Glasgow Microenvironment Score (GMS): This simplified prognostic tool evaluates the tumor microenvironment by integrating the KM grade and the TSR to stratify patients into three prognostic groups. The GMS Grading Scale will assign patients to GMS 0 (high-grade inflammatory response), GMS 1 (low-grade inflammatory response with low stromal percentage), or GMS 2 (low-grade inflammatory response with a high stromal percentage).

Inclusion Criteria:

• Patients who underwent radical cystectomy for muscle invasive urothelial carcinoma.
• Treated at the South Egypt Cancer Institute (SECI) between 2018 and 2024.

Exclusion Criteria:

• Cases with non-urothelial histological subtypes (e.g., pure squamous cell carcinoma).
• Patients who received neoadjuvant chemotherapy or radiotherapy.
• Cases with missing or inaccessible clinical follow-up data.
• History of prior or concurrent malignancy.