Circulating tumor microemboli (CTM) aggregated by ≥ 2 circulating tumor cells (CTCs) are more migratory than single CTCs. Aside from the plasticity in their molecular characteristics, which have been considered tumor migration, CTM also possesses high size heterogeneity. This study, therefore, systematically investigated the heterogeneous sizes of CTM and their involvement in therapeutic resistance in 114 patients with advanced gastric cancer (GC) using a pre-established surface molecule-independent subtraction enrichment (SE)-iFISH strategy. CTM, which was pre-therapeutically detected in 33.3% of GC patients, can further form in another 34.78% of patients following chemo-/targeted therapies. The presence of CTM is relevant to liver metastasis as well as higher CTC levels (≥ 5/6 mL). Further size-based profiling of GC-CTM revealed that CTM with 2 CTCs (CTM₂) was the dominant subtype, accounting for 50.0% of all detected GC-CTMs. However, CTM with 3–4 CTCs (CTM_3–4) specifically associates with chemo-/targeted therapeutic resistance and inferior prognosis. Patients with ≥ 1 CTM_3–4/6 mL have shorter median progression-free survival and median overall survival. Unlike CTM₂ and CTM_3–4, which are detectable in pre-therapy and post-therapy, larger aggregated CTM_≥5 (CTM with ≥ 5 CTCs) was only intra-therapeutically detected in four HER2⁺ GC patients, of which three experienced liver metastases. Obtained results suggested that the cluster size of GC-CTM should be dynamically profiled beyond pre-therapeutic whole CTM enumeration in terms of chemo-/targeted resistance or metastasis monitoring. GC-CTM_3–4 could be a potential indicator of therapeutic resistance, while the dynamic presence of GC-CTM_≥5 implies liver metastasis in HER2⁺ GC patients.

由 ≥ 2 个循环肿瘤细胞 (CTC) 聚集的循环肿瘤微栓子 (CTM) 比单个 CTC 更具迁移性。除了被认为是肿瘤迁移的分子特征的可塑性外，CTM 还具有高度的异质性。因此，本研究使用预先建立的表面分子独立减法富集 (SE)-iFISH 策略系统地研究了 CTM 的异质大小及其在 114 名晚期胃癌 (GC) 患者中的治疗耐药性。CTM 在 33.3% 的 GC 患者中进行治疗前检测到，在另外 34.78% 的化疗/靶向治疗后的患者中可进一步形成。CTM 的存在与肝转移以及更高的 CTC 水平（≥ 5/6 mL）有关。₂ ) 是主要亚型，占所有检测到的 GC-CTM 的 50.0%。然而，具有 3-4 个 CTC（CTM _3-4）的CTM与化疗/靶向治疗耐药性和较差的预后特别相关。≥ 1 CTM _3-4 /6 mL患者的中位无进展生存期和中位总生存期较短。不同于CTM ₂和CTM _3-4，其是在治疗前和治疗后检测的，较大的聚集CTM _≥5（CTM与≥5的CTC）是仅-治疗帧内四个HER2检测⁺GC 患者，其中 3 例发生肝转移。获得的结果表明，在化疗/靶向耐药或转移监测方面，GC-CTM 的簇大小应该在治疗前的整个 CTM 枚举之外进行动态分析。GC-CTM _3-4可能是治疗耐药性的潜在指标，而 GC-CTM _≥5的动态存在意味着 HER2 ⁺ GC 患者的肝转移。