Abstract 1176P
Background
Small cell carcinoma of the esophagus (SCCE) is a rare but highly aggressive neuroendocrine carcinoma. Despite aggressive initial therapy, most patients with SCCE suffer a rapid recurrence and die within a few months. Given the great success of cancer immunotherapy targeting the PD-1/PD-L1 pathway, we sought to assess the expression pattern and clinical significance of PD-L1 in previously untreated SCCE for the first time.
Methods
Formalin-fixed paraffin-embedded whole tumor sections were obtained from 147 patients with SCCE underwent surgery at our institution between 1985 and 2019. PD-L1 expression was evaluated by immunohistochemistry (clone E1L3N) in both tumor cells (TCs) and tumor-infiltrating immune cells (ICs). PD-L1 positivity (PD-L1+) was defined as ≥1% TCs with circumferential or partial membranous staining, or ICs with membranous or cytoplasmic staining. A combined positive score (CPS) of PD-L1 expression was also calculated and CPS ≥1 was considered positive. Baseline clinicopathological characteristics and outcome data [relapse free survival (RFS) and overall survival (OS)] were correlated with PD-L1 staining.
Results
None of the 147 patients was considered PD-L1+ in TCs and PD-L1+ in ICs was observed in 65 (44.2%) patients. Forty-two (28.6%) patients showed CPS positivity. PD-L1+ in ICs was significantly associated with shorter tumor length (P=0.003), macroscopic tumor type (P=0.011), and lower T stage (P=0.028), as well as increased RFS (P=0.0099) and OS (P=0.0005). PD-L1+ by CPS was also found significantly correlated with shorter tumor length (P=0.014), macroscopic tumor type (P=0.015), and lower T stage (P<0.001), as well as better OS (P=0.0453). Whereas, only a trend toward longer RFS (P=0.0671) was observed in patients with CPS positivity.
Conclusions
Here, for the first time, we showed that approximately half of the SCCEs express PD-L1 and all the expression is observed in immune cells. Patients with PD-L1 expression are associated with early stage and better survival. These data provide a rational basis for further investigation of PD-L1/PD-1-based immunotherapy for patients with SCCE.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College.
Funding
Chinese Academy of Medical Sciences.
Disclosure
All authors have declared no conflicts of interest.