PD-L1 Expression in Paired Samples of Rectal Cancer

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Immune checkpoint inhibitors are crucial in cancer therapy.
• Biomarkers like PD-L1 are vital for predicting treatment response in rectal cancer (RC).
• Understanding PD-L1 expression dynamics in RC is essential for optimizing treatment strategies.

Purpose of the Study:

• To analyze programmed death-ligand 1 (PD-L1) expression in diagnostic biopsy and resection samples from rectal cancer patients.
• To evaluate the correlation between PD-L1 expression levels and patient outcomes.
• To investigate the impact of neoadjuvant therapy on PD-L1 expression in RC.

Main Methods:

• Retrospective analysis of 83 rectal cancer patients treated between 2000 and 2020.
• PD-L1 immunostaining (22C3 clone) assessed using tumor proportion (TPS), immune cell (ICS), and combined positive score (CPS).
• Comparison of PD-L1 expression between biopsy and surgical samples, and correlation with disease-free survival (DFS) and overall survival (OS).

Main Results:

• PD-L1 expression, particularly ICS, was significantly lower in surgical samples compared to biopsy samples (p ≤ 0.04).
• Neoadjuvant chemoradiotherapy led to a reduction in PD-L1-ICS (p = 0.03).
• Elevated PD-L1-ICS in surgical samples (≥5%) and a biopsy-to-surgery increase in PD-L1-ICS independently predicted longer DFS and better OS.

Conclusions:

• PD-L1 expression in rectal cancer primarily reflects immune cell infiltration.
• PD-L1 immune cell staining in surgical samples, or an increase from biopsy to surgery, is a significant predictor of favorable prognosis in RC patients.
• These findings support the utility of PD-L1 assessment in guiding rectal cancer treatment and predicting patient outcomes.