In biliary tract cancer (BTC), tissue biopsies to guide treatment are rarely feasible, thus implementing liquid biopsy approaches to improve patient management represents a priority. So far, studies on circulating tumor cells (CTCs) in BTC are insufficient to promote their use in patient clinical management and are limited to EpCAM-enriched CTCs evaluated with the CellSearch. We applied a single-cell protocol allowing identification not only of epithelial CTCs (eCTCs), but also of nonconventional CTCs (ncCTCs) lacking epithelial and leukocyte markers, but presenting aberrant genomes as confirmed by copy number alterations and therefore representing a distinct subpopulation of bona fide CTCs. In 41 blood samples longitudinally collected from 21 patients with advanced-stage BTC, addition of ncCTC to classic eCTC led to a CTC-positivity increase from 19% to 83%. Patients presenting with at least 1 eCTC/10 ml of blood at baseline prior to treatment start had a significantly shorter median disease-specific survival (DSS) compared to those lacking eCTCs (9 months vs. 19 months, p = 0.03 by log-rank test). No differences in DSS were observed according to ncCTC-positivity, conversely, variations in ncCTC counts during, and at the end of treatment, were associated with the RECIST response supporting their role in treatment monitoring. Moreover, in 88 ncCTCs collected at different times during treatment, unsupervised clustering evidenced segregation of cells by patient's best response, allowing identification of genomic regions possibly involved in resistance mechanisms. The presence of ncCTCs beside eCTCs opens the way to exploiting liquid biopsy for optimizing clinical management in BTC.

中文翻译：

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一种新型的循环肿瘤细胞亚群，用于胆道癌的治疗监测和分子表征。

在胆道癌（BTC）中，指导治疗的组织活检很少可行，因此实施液体活检方法以改善患者管理成为当务之急。到目前为止，对BTC中循环肿瘤细胞（CTC）的研究不足以促进其在患者临床管理中的应用，并且仅限于用CellSearch评估的富含EpCAM的CTC。我们应用了单细胞方案，不仅可以鉴定上皮CTC（eCTC），而且还可以鉴定缺乏上皮和白细胞标记的非常规CTC（ncCTC），但是可以通过拷贝数变化证实存在异常的基因组，因此代表了bona的不同亚群真正的CTC。从21例晚期BTC患者的纵向采集的41份血液样本中，在经典eCTC中添加ncCTC导致CTC阳性率从19％增加到83％。与没有eCTC的患者相比，治疗开始前在基线时至少有1 eCTC / 10 ml血液的患者的中位疾病特异性生存（DSS）明显短（9个月比19个月，p = 0.03，按对数排序）测试）。根据ncCTC阳性，未观察到DSS的差异，相反，治疗期间和治疗结束时ncCTC计数的变化与RECIST反应相关，支持了其在治疗监测中的作用。此外，在治疗期间的不同时间收集的88个ncCTC中，无监督的聚类可通过患者的最佳反应证明细胞分离，从而可以鉴定可能参与耐药机制的基因组区域。