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Tumor response and disease progression are assessed using imaging technologies. However, these technologies fail to detect tumor responses at the molecular level and clonal evolution. A potential surrogate for such parameters is using circulating tumor DNA (ctDNA). This study aimed to examine the quantity and composition of the ctDNA results of 29 cancer patients before and after dendritic cell (DC) immunotherapy and develop criteria to evaluate the molecular response to treatment based on these results. We categorized the patients into four categories based on percent changes in the total ctDNA compared with the baseline ctDNA titers, and this response assessment was termed genomic response evaluation criteria in solid tumors or gRECIST. Even those who are clinically evaluated as having a good response might harbor unfavorable tumor responses at the molecular level. Newly formed ctDNA levels can be the most prognostic parameter in tumor progression or the treatment response, while ctDNA clearance and the decline or rise in existing ctDNA did not change significantly in genomic response categories (gRECIST). More research is needed to support the clinical use of ctDNA in precision oncology and personalized cancer treatment.

Liquid biopsies can be a rapid, cost-effective and noninvasive alternative to tumor biopsies for detecting genetic mutations in somatic tumors. Genetic profiling of liquid biopsies can also be used to identify novel antigens for targeted therapy, provide updated information on disease prognosis and evaluate treatment efficacy. In this study, we aimed to examine mutations that could be identified in liquid biopsy and their potential implications for personalized dendritic cell immunotherapy using neoantigens. We analyzed the genomic profiles of 99 blood samples from 85 patients with 22 different types of cancer using two commercially available liquid biopsy tests before the patients underwent standard cancer treatment and dendritic cell immunotherapy. Nonsynonymous mutations were detected in more than 90% of the samples, with an average frequency of 3.6 mutations per sample. The tumor mutations were specific to each patient, as approximately 94.7% of the mutations were so unique that there was almost no duplication among the patients. Clonal evolution was observed in two patients just before or after chemotherapy, radiotherapy and immunotherapy. These findings indicate that liquid biopsy can be a potential surrogate for neoantigen-based immunotherapy and the importance of tailoring neoantigen-based immunotherapy in accordance with the liquid biopsy result in each treatment stage.