PMC9528799_01
Clinical course of the patient. (A) Serial PET/CT images of primary tumor lesion, liver metastasis, abdominal lymph node metastasis and reconstruction of coronal plane at different stages of treatment; (B) Timeline of clinical events. (C) Level of CA199 during the treatment.
CMAR-14-2927-g0001.jpg
PMC9528799_01_CMAR-14-2927-g0001.jpg
f0001
Multiple lymph node metastasis, liver metastasis and lumbar metastasis (L5) were also identified (Figure 1A). The tumor biomarker CA199 was even higher after first cycle chemotherapy (Figure 1C) without any relief of his symptoms. Within one month, his tumor markers dramatically improved with remission of clinical symptoms (Figure 1C). Due to renal dysfunction, the patient performed FDG-PET/CT scan for treatment efficacy assessment, which showed significantly decreased FDG uptake of multiple metastatic sites in May 2020 (Figure 1A). The third-line treatment with the PD-1 inhibitor tislelizumab (200mg every three weeks) was next started but the disease progressed after 2 months (Figure 1A). ctDNA was collected in August 2020 and ERBB2 p.V842I with an allele frequency of 2.06% was identified by NGS. PET/CT evaluation revealed disease progression in March 2021, and the treatment was then discontinued (Figure 1A).
Dynamic profiling of somatic mutations in ctDNA.
CMAR-14-2927-g0002.jpg
PMC9528799_01_CMAR-14-2927-g0002.jpg
f0002
Then, next-generation sequencing (NGS) by a commercial laboratory (Genecast Biotechnology Co., Ltd, Jiangsu, China) identified ERBB2 p.V842I in both circulating tumor DNA (ctDNA) and biopsy sample with an allele frequency of 3.94% and 26.07%, respectively (Figure 2).   Dynamic monitoring of the ctDNA again confirmed ERBB2 p.V842I by NGS with a lower allele frequency of 0.41% (Figure 2).