Immune-Checkpoint Inhibition in the Treatment of Gastro-Esophageal Cancer: A Closer Look at the Emerging Evidence

To date, several trials have evaluated the safety and efficacy of immune-checkpoint inhibitors (ICI) for the treatment of gastroesophageal cancers (GEC). In the US, ICIs have established indications for second-line treatment of microsatellite unstable tumors, while their use in third-line settings was recently withdrawn. Notably, the use of ICIs for first-line therapy of GEC is rapidly evolving, which currently includes high PD-L1 expressing tumors, irrespective of HER2 status, and in the adjuvant setting after neoadjuvant chemoradiotherapy in select patients. In this article, we review the results of studies that have evaluated the utility of ICI in the third-line, second-line, first-line, and peri-operative treatment settings of GECs. Considerations should be made before making any cross-trial comparisons since these trials vary in chemotherapy backbone, anatomical and histological eligibility, biomarker assessment, PD-L1 diagnostic antibodies, and definition of PD-L1 positivity. Regardless, the totality of the data suggest that first-line ICI use may most benefit GEC patients with high PD-L1 combined positivity score (CPS) ≥5 or ≥10, irrespective of histology or anatomy. Moreover, although PD-L1 by CPS has a good negative predictive value for significant benefit from ICIs, it has a low positive predictive value. Therefore, there is a pressing need to identify better biomarkers to predict benefit from ICIs among these patients.

Combination regimens with PD-1/PD-L1 immune checkpoint inhibitors for gastrointestinal malignancies

Gastrointestinal (GI) malignant neoplasms have a high global incidence and treatment prospects for patients with advanced GI tumors are dismal. PD-1/PD-L1 inhibitors emerged as a frontline treatment for several types of cancer. However, the shortcomings of PD-1/PD-L1 inhibitors have been observed, including low objective response rates and acquired tumor resistance, especially in patients receiving PD-1/PD-L1 inhibitors as a single treatment. Accumulating evidence from clinical trials increasingly suggests that combined immunotherapies enhance therapeutic responses in patients with malignances, especially for GI tumors which have a complex matrix, and significant molecular and immunological differences. Preclinical and clinical studies suggest there are advantages to combined immunological regimens, which represents the next logical step in this field, although further research is necessary. This literature review explores the current limitations of monotherapies, before critically discussing the rationale behind combination regimens. Then, we provide a summary of the clinical applications for gastrointestinal cancers.

Efficacy and safety of immune checkpoint inhibitors in advanced gastric or gastroesophageal junction cancer: a systematic review and meta-analysis

Background: Immune checkpoint inhibitors (ICI) have shown promising prospects in gastroesophageal junction (G/GEJ) cancer immunotherapy, many clinical trials have been carried out. Objective: To evaluate the efficacy and safety of ICI in G/GEJ cancer. Methods: The published English articles of PubMed, Cochrane Library, Embase, Web of Science were searched up to 30/09/2018. The efficacy and safety of ICI were analyzed by meta-analysis. Results: A total of 2003 patients from nine clinical trials were included. Anti-PD-1 treatment improved the 12-month, 18-month overall survival (OS) rate (RR, 1.79 p = 0.013; 2.20 p = 0.011) and prolonged the duration of response (DOR) (MSR, 3.27 p < 0.001). The objective response rate (ORR) in PD-L1+ patients was greater than PD-L1- (RR, 4.31 p < 0.001). Microsatellite instability-high (MSI-H) patients had higher ORR and disease control rate (DCR) than microsatellite stability (MSS) (RR, 3.40 p< 0.001; 2.26 p= 0.001). The most common grade ≥3 treatment-related adverse events (TRAEs) were fatigue, aspartate aminotransferase increased, hepatitis, pneumonitis, colitis, hypopituitarism. The TRAE incidence of anti-PD-1/PD-L1 was less than chemotherapy (TRAE RR = 0.64 p< 0.001; ≥3 TRAE RR = 0.37 p < 0.001). The incidence of ≥3 TRAEs of anti-PD-1/PD-L1 treatment was less than that of anti-CTLA-4 (11.7% vs 43.9%). Conclusions: ICI treatment could improve some but not all survival endpoints to advanced or metastatic G/GEJ cancer patients suggesting modest benefit and less adverse reactions. Anti-PD-1/PD-L1 therapy was more effective to PD-L1+, MSI-H, EBV+, or high tumor mutational burden patients.

Immunotherapy in Esophagogastric Adenocarcinoma

Immunotherapy, particular PD-1/L1 inhibition, is a relevant treatment approach in esophagogastric adenocarcinoma. To date, single-agent activity is limited to the chemotherapy refractory setting and molecularly defined subgroups. Currently, ongoing trials, which are likely to relevantly change the landscape of treatment for this disease in the next years, evaluate different combination approaches with chemotherapy and/or molecular targeted agents in different disease settings. The German AIO study group has launched several combination trials in the perioperative, first-line, and advanced disease setting to further define the role of immunotherapy in esophagogastric adenocarcinoma.