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Updated: Feb 15, 2026

Development of a 68Gallium-Labeled D-Peptide PET Tracer for Imaging Programmed Death-Ligand 1 Expression
Published on: February 3, 2023
Pattern of programmed cell death-ligand 1 expression and CD8-positive T-cell infiltration before and after
Atsushi Ogura1, Takashi Akiyoshi2, Noriko Yamamoto3
1Department of Gastroenterological Surgery, Cancer Institute Hospital of Japanese Foundation for Cancer Research, 3-8-31, Ariake, Koto-ku, Tokyo 135-8550, Japan; Division of Surgical Oncology, Department of Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Background:
The synergistic effect of combining immune checkpoint inhibitors with radiotherapy was reported recently, but there are few studies on programmed cell death-ligand 1 (PD-L1) expression in rectal cancer treated by preoperative chemoradiotherapy (CRT). The aim of the present study was to investigate the PD-L1 expression status before and after CRT and its association with clinicopathological characteristics and recurrence in rectal cancer.
Methods:
Immunostainings of PD-L1 and CD8 were performed in 287 patients with rectal cancer treated by CRT. PD-L1 expression on the tumour cells (tPD-L1) and on the stromal immune cells (iPD-L1) was evaluated before and after CRT. CD8+ cell density in tumour area (tCD8+) before CRT and in the stromal area (sCD8+) before and after CRT was also evaluated.
Results:
High tPD-L1 expression was observed in only three patients (1.0%). High iPD-L1 expression significantly increased from 31.7% before CRT to 49.2% after CRT (P < 0.0001). The increase in high iPD-L1 expression after CRT was only observed in patients with tumour regression grades 1 and 2. High iPD-L1 expression was associated with high tCD8+ cell density before CRT (P < 0.0001) and sCD8+ cell density after CRT (P < 0.0001). High tCD8+ cell density before CRT was associated with better disease-free survival (DFS) (P = 0.0331), but its improved effect on DFS could be observed in patients with high iPD-L1 expression (P = 0.0081), not in patients with low iPD-L1 expression (P = 0.516).
Conclusion:
The present study demonstrated the significant correlations between iPD-L1 expression and CD8+ cell density both before and after CRT.
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