Abstract
Immunotherapy, represented by immune checkpoint inhibitors (mainly referring to programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) blockades), derives durable remission and survival benefits for multiple tumor types including digestive system tumors [gastric cancer (GC), colorectal cancer (CRC), and hepatocellular carcinoma (HCC)], particularly those with metastatic or recurrent lesions. Even so, not all patients would respond well to anti-programmed death-1/programmed death-ligand 1 agents (anti-PD-1/PD-L1) in gastrointestinal malignancies, suggesting the need for biomarkers to identify the responders and non-responders, as well as to predict the clinical outcomes. PD-L1expression has increasingly emerged as a potential biomarker when predicting the immunotherapy-based efficacy; but regrettably, PD-L1 alone is not sufficient to differentiate patients. Other molecules, such as tumor mutational burden (TMB), microsatellite instability (MSI), and circulating tumor DNA (ctDNA) as well, are involved in further explorations. Overall, there are not still no perfect or well-established biomarkers in immunotherapy for digestive system tumors at present as a result of the inherent limitations, especially for HCC. Standardizing and harmonizing the assessments of existing biomarkers, and meanwhile, switching to other novel biomarkers are presumably wise and feasible.
Highlights
As mentioned in real-world investigations, the application of immunotherapy has obtained great success in multiple tumor types, increasingly shifting the conventional treatment paradigm to precision and individual medicine [1,2,3]
An excellent and durable clinical response to immunotherapy could be undoubtedly seen in patients with cancer; but the fact is, based on the initial data from the last few decades, the response rate always reached
Even when utilizing the same biomarkers, different predictive results are common across various immune checkpoint inhibitors (ICIs) and distinct cancer types; in other words, these molecules are subject to their innate limitations, as well as the bioinformatic-technique and personnel errors
Summary
As mentioned in real-world investigations, the application of immunotherapy has obtained great success in multiple tumor types, increasingly shifting the conventional treatment paradigm to precision and individual medicine [1,2,3]. TMB seems to be a valid predictor of response to ICIs-based immunotherapy for EC, GC, and CRC, but its status remains further confirmed as the current trials are almost small samples, and there are no large-scale and phase III clinical studies to verify them.
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