Prognostic relevance of programmed death-ligand 1 expression and microsatellite status in small bowel adenocarcinoma

Immune signature of small bowel adenocarcinoma and the role of tumor microenvironment

In this editorial we comment on the article published "Clinical significance of programmed cell death-ligand expression in small bowel adenocarcinoma is determined by the tumor microenvironment". Small bowel adenocarcinoma (SBA) is a rare gastrointestinal neoplasm and despite the small intestine's significant surface area, SBA accounts for less than 3% of such tumors. Early detection is challenging and the reason arises from its asymptomatic nature, often leading to late-stage discovery and poor prognosis. Treatment involves platinum-based chemotherapy with a 5-fluorouracil combination, but the lack of effective chemotherapy contributes to a generally poor prognosis. SBAs are linked to genetic disorders and risk factors, including chronic inflammatory conditions. The unique characteristics of the small bowel, such as rapid cell renewal and an active immune system, contributes to the rarity of these tumors as well as the high intratumoral infiltration of immune cells is associated with a favorable prognosis. Programmed cell death-ligand 1 (PD-L1) expression varies across different cancers, with potential discrepancies in its prognostic value. Microsatellite instability (MSI) in SBA is associated with a high tumor mutational burden, affecting the prognosis and response to immunotherapy. The presence of PD-L1 and programmed cell death 1, along with tumor-infiltrating lymphocytes, plays a crucial role in the complex microenvironment of SBA and contributes to a more favorable prognosis, especially in the context of high MSI tumors. Stromal tumor-infiltrating lymphocytes are identified as independent prognostic indicators and the association between MSI status and a favorable prognosis, emphasizes the importance of evaluating the immune status of tumors for treatment decisions.

PD-L1 evaluation in the gastrointestinal tract: from biological rationale to its clinical application

Immune-checkpoint inhibitors targeting the PD-1/PD-L1 axis have brought significant clinical benefit in many solid cancer types, including gastrointestinal malignancies. However, it has been estimated that only 20-40% of patients respond to treatment. The pattern of expression and potential predictive value of PD-L1 as an immunohistochemical biomarker has been extensively studied in gastrointestinal neoplasms. Until now, its predictive value has been demonstrated, and is currently in use only in upper gastrointestinal malignancies (gastroesophageal adenocarcinoma and esophageal squamous cell carcinoma).

In this Review, we describe the technical aspects and challenges related to PD-L1 immunohistochemical assays, the current role of PD-L1 as a biomarker in clinical practice and we outline the main studies and clinical trials analyzing the prognostic and predictive value of PD-L1 in gastrointestinal cancers.

Systemic Therapy for Microsatellite Instability Small Bowel Adenocarcinoma With Mesenteric Vascular Embolism as Initial Symptom: A Case Report

Background: Small bowel adenocarcinoma are relatively rare tumors of the digestive system. Due to the lack of specific screening methods, patients are often diagnosed at an advanced stage. At present, there is no specific surgical guidance and chemotherapy regimen for small bowel adenocarcinoma. Here, we report a rare small bowel adenocarcinoma case with mesenteric vascular embolization and microsatellite instability, in which palliative surgery combined with chemotherapy and anti-Programmed cell death protein 1(PD-1) therapy resulted in complete remission.

Case Presentation: The patient was a 55-year-old man who was admitted for suspected small bowel adenocarcinoma combined with incomplete ileus, mesenteric vascular occlusion and distant metastasis. We performed palliative surgery to remove adenocarcinoma as well as relieve obstruction. Then according to the pathological and immunohistochemical results (Stage IV and microsatellite instability), we used XELOX regimen combined with anti-PD-1 therapy. In last 2 years follow up, this patient achieved complete remission.

Conclusions: The possibility of small intestinal tumor should be considered in patients with mesenteric vascular obstruction. PD-1 blockade is an effective therapy for small bowel adenocarcinoma with microsatellite instability.