Background: Tumor of the digestive system is a common malignancy with high morbidity and mortality. Although programmed cell death-1 (PD-1) inhibitors have become an effective treatment strategies for many kinds of tumors, there is still some uncertainty in digestive tumors, including: (I) therapeutic effects of PD-1 inhibitors are relatively limited; (II) responses of digestive system tumors to immunotherapies are highly heterogeneous. In the present study, we investigated the outcomes of PD-1 inhibitors for digestive system tumors in Chinese patients to analyze factors that may affect the effects of immunotherapies in digestive system tumors.
Methods: Data were obtained from the Hospital Information System (HIS) of the Department of Digestive Oncology (Henan Cancer Hospital) between January 2019 and December 2019. Inclusion criteria included patients receiving the same PD-1 inhibitor continuously for advanced or recurrent/metastatic digestive system tumors. Indicators including age, sex, clinical diagnosis, height, weight, gene status, PD-1 inhibitors, treatment regimen, medication cycle, efficacy evaluation results, and adverse reactions were analyzed retrospectively. The clinical outcomes were progression-free survival (PFS) and safety.
Results: A total of 2,767 patients were discharged from HIS, of which 64 (37 male/27 female) were included in this study. Thirty-eight (59.4%) of the patients were aged <60 years. Tumors included esophageal, gastric, liver, colorectal, and pancreatic cancer. Up until 30 June 2020, 51 patients were followed up to median progression-free survival (PFS), which was 5 months; the longest PFS was 18.5 months. There was no statistical significance in grouping according to sex, age and body mass index. Nevertheless, the median PFS differed statistically between monotherapy (9.4 months) versus combined therapy (4.7 months), and Cox regression analysis suggested that patients might benefit more from monotherapy than combined therapy. The incidence of adverse reactions was 47.7%, with thyroid dysfunction the most common adverse reaction. The incidence of grade 3-4 adverse reactions was 9.2% and mainly included pulmonary infection, immune-associated hepatitis, and severe oral ulcers.
Conclusions: In digestive tumors, especially for second-line treatment and beyond, PD-1 monotherapy might be more beneficial than combined therapy. However, this might be related to the patient's tolerance. Large-sample prospective studies are needed for confirmation.
Keywords: Immune checkpoint inhibitor (ICI); PD-1 monotherapy; adverse reactions; digestive system tumors.