Source:European Journal of Cancer, Volume 91
Author(s): Atsushi Ogura, Takashi Akiyoshi, Noriko Yamamoto, Hiroshi Kawachi, Yuichi Ishikawa, Seiichi Mori, Koji Oba, Masato Nagino, Yosuke Fukunaga, Masashi Ueno
BackgroundThe 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.MethodsImmunostainings 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.ResultsHigh 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).ConclusionThe present study demonstrated the significant correlations between iPD-L1 expression and CD8+ cell density both before and after CRT.
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