Comment on: Jilkova, Z.M.; et al. “Predictive Factors for Response to PD-1/PD-L1 Checkpoint Inhibition in the Field of Hepatocellular Carcinoma: Current Status and Challenges” Cancers 2019, 11, 1554

I read with interest the article ‘Predictive Factors for Response to PD-1/PD-L1 Checkpoint Inhibition in the Field of Hepatocellular Carcinoma: Current Status and Challenges’ [1]. However, the authors’ assertion that ‘Certainly, high TMB and neoantigen load have been noted to predict the response to immunotherapies, including anti-PD-1 therapy (higher objective response rate and/or prolonged survival) in melanoma, non-small-cell lung carcinoma’ is not supported by the reference provided—an article by Topalian et al. [2]—which mentions neither tumour mutational burden (TMB) nor neoantigen load. A better reference might have been a retrospective review published by Goodman et al. in 2017 [3] in which 151 immunotherapy-treated patients who had undergone TMB assessment were analysed, and a linear correlation between higher TMB and better outcome parameters was identified. Nonetheless, I would also suggest that a definitive conclusion should not be based purely on a retrospective review in any case, and that a prospective study or clinical trial is needed to support inferences about the ability of TMB to predict response to PD-1 inhibitors.