PD-L1 expression, CD8+ and CD4+ lymphocyte rate are predictive of pathological complete response after neoadjuvant chemoradiotherapy for squamous cell cancer of the thoracic esophagus

Abstract

Background: Neoadjuvant chemoradiotherapy (CTRT) can effectively downstage esophageal squamous cell carcinoma (SCC) in patients with locally advanced disease and prolonged survival have been observed in patients with a pathological complete response (ypCR).

Aims and methods: This exploratory study aimed to identify immunological predictors of pCR after neoadjuvant CTRT within SCC microenvironment. The tumor regression after neoadjuvant therapy was measured according to the Mandard score system. Eighty-eight consecutive patients with SCC of the thoracic esophagus who received neoadjuvant CTRT were included in this retrospective study. Inclusion criteria were neoadjuvant CTRT and the availability of representative histological samples taken at diagnosis. We investigated immunohistochemical expression of CD4, Tbet, FoxP3, CD8, CD80, PD-L1, and PD-1, in the pretreatment biopsies and correlated the immunohistochemical profiles to patients' outcomes.

Results: After neoadjuvant CTRT, 23 patients had pCR, while 65 ones had partial response, stable disease or progression. PD-L1 expression and CD8+ and CD4+ lymphocyte rate were significantly higher in patients who had ypCR compared to those who had not (10 (0-55) vs 0 (0-0), P = 0.004, 73 (36-147) vs 21 (7-47), P = 0.0006 and 39 (23-74) vs 5 (0-13), P < 0.0001 respectively). The accuracy of expression of PD-L1+, CD8+, and CD4+ lymphocyte rate in identifying responders was AUC = 0.76 (P = 0.001), AUC = 0.81 (P = 0.0001) and AUC = 0.75 (P = 0.0001), respectively. Within the ypCR group, all patients with high infiltration of CD4+ T cell recurred/relapsed while only the 38.9% of those with low CD4+ T cell infiltration did the same (P = 0.058).

Conclusions: PD-L1 expression and CD8+ and CD4+ lymphocyte rate were predictive of ypCR after neoadjuvant CTRT for SCC of the thoracic esophagus with adequate accuracy. Furthermore, recurrence/relapse was associated with high level of CD4+ T cell infiltration. However, the small sample size prevented to draw definitive conclusions; further studies are necessary to evaluate the prognostic role of these markers.

Keywords: esophageal cancer; induction chemoradiotherapy; neoadjuvant therapy; squamous cell carcinoma; survival analysis.

Figure 1

Flowchart of included patients. Abbreviations: PPD: persistence or progressive disease (as opposed to yCR). SCC: esophageal squamous cell carcinoma.

Figure 2

Immunological predictors of clinical outcome after neoadjuvant CT‐RT in esophageal squamous cell carcinoma. PD‐L1, CD80, CD4, CD8 expression in yCR and yPPD tumors according to response to neoadjuvant therapy in the whole cohort (A) and in clinical stage III‐IV tumors treated with DDP ± 5FU (B). Data are shown as. Min‐Max error bars and Mann‐Whitney test was used for the comparison. (C) Representative examples of immunohistochemical stainings of PD‐L1, CD4 and CD8 according to tumor responsiveness to neoadjuvant therapy (original magnifications 20×, scale bar = 100 µm).

Figure 3

(A) ROC curves for yCR or *yPPD after neoadjuvant therapy; (B) ROC curves for FoxP3 and Tbet as predictor of yCR after neoadjuvant therapy. The accuracy of immunological markers as predictors of yCR was tested in the subgroup of patients with the ROC curve analysis.

Figure 4

Tumor immune infiltrate as predictor of overall survival. The Kaplan‐Meier estimate was used to perform the survival analysis from the date of the initial diagnosis and the log‐rank test was used to compare the subgroup survival.