BACKGROUND & AIMS Biomarkers are needed to risk stratify after chemoradiotherapy for localized esophageal cancer. These could improve identification of patients at risk for cancer progression and selection of additional therapy. METHODS We performed deep sequencing (CAncer Personalized Profiling by deep Sequencing, [CAPP-Seq]) analyses of plasma cell-free DNA collected from 45 patients before and after chemoradiotherapy for esophageal cancer, as well as DNA from leukocytes and fixed esophageal tumor biopsy samples collected during esophagogastroduodenoscopy. Patients were treated from May 2010 through October 2015; 23 patients subsequently underwent esophagectomy, and 22 did not undergo surgery. We also sequenced DNA from blood samples from 40 healthy control individuals. We analyzed 802 regions of 607 genes for single-nucleotide variants previously associated with esophageal adenocarcinoma or squamous cell carcinoma. Patients underwent imaging analyses 6-8 weeks after chemoradiotherapy and were followed for 5 years. Our primary aim was to determine whether detection of circulating tumor DNA (ctDNA) after chemoradiotherapy is associated with risk of tumor progression (growth of local, regional, or distant tumors, detected by imaging or biopsy). RESULTS The median proportion of tumor-derived DNA in total cell-free DNA before treatment was 0.07%, indicating that ultrasensitive assays are needed for quantification and analysis of ctDNA from localized esophageal tumors. Detection of ctDNA after chemoradiotherapy was associated with tumor progression (hazard ratio, 18.7; P < .0001), formation of distant metastases (hazard ratio, 32.1; P < .0001), and shorter disease-specific survival times (hazard ratio, 23.1; P < .0001). A higher proportion of patients with tumor progression had new mutations detected in plasma samples collected after chemoradiotherapy than patients without progression (P = .03). Detection of ctDNA after chemoradiotherapy preceded radiographic evidence of tumor progression by an average of 2.8 months. Among patients who received chemoradiotherapy without surgery, combined ctDNA and metabolic imaging analysis predicted progression in 100% of patients with tumor progression, compared with 71% for only ctDNA detection and 57% for only metabolic imaging analysis (P < .001 for comparison of either technique to combined analysis). CONCLUSIONS In an analysis of cell-free DNA in blood samples from patients who underwent chemoradiotherapy for esophageal cancer, detection of ctDNA was associated with tumor progression, metastasis, and disease-specific survival. Analysis of ctDNA might be used to identify patients at highest risk for tumor progression.

中文翻译：

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循环肿瘤DNA分析检测局部食管癌放化疗后的微小残留疾病。

背景与目的在局部食管癌的放化疗后，需要生物标志物进行分层风险。这些可以改善对有癌症进展风险的患者的识别和选择其他治疗方法。方法我们对食管癌放化疗前后从45例患者中收集的无血浆细胞DNA以及从白细胞和固定的食管肿瘤活检样品中提取的血浆无细胞DNA进行了深度测序（CAncer个性化分析，通过深度测序，[CAPP-Seq]）在食管胃十二指肠镜检查中收集。从2010年5月至2015年10月对患者进行了治疗；随后有23例患者接受了食管切除术，其中22例未接受手术。我们还对40个健康对照者的血液样本中的DNA进行了测序。我们分析了607个基因的802个区域中先前与食管腺癌或鳞状细胞癌相关的单核苷酸变异。放化疗后6-8周对患者进行影像学分析，并随访5年。我们的主要目的是确定放化疗后循环肿瘤DNA（ctDNA）的检测是否与肿瘤进展的风险（通过成像或活检检测到的局部，区域或远处肿瘤的生长）有关。结果治疗前无源DNA中肿瘤来源的DNA的中位比例为0.07％，表明需要定量和分析食管癌中ctDNA的超灵敏测定。放化疗后检测到的ctDNA与肿瘤进展有关（危险比，18.7； P <.0001），远处转移的形成（危险比，32.1； P <.0001）和较短的疾病特异性生存时间（危险比，23.1； P <.0001）。与没有进展的患者相比，在放化疗后收集的血浆样本中发现具有肿瘤进展的患者比例更高（P = .03）。化学放疗后对ctDNA的检测在影像学证据显示肿瘤进展之前平均需要2.8个月。在未经手术放化疗的患者中，ctDNA和代谢成像分析相结合可预测100％肿瘤进展的患者的进展，相比之下，仅ctDNA检测的患者为71％，仅代谢成像分析的为57％（两者比较的P <.001组合分析技术）。结论在对食管癌进行放化疗的患者血液样本中的无细胞DNA分析中，ctDNA的检测与肿瘤的进展，转移和疾病特异性生存有关。ctDNA的分析可用于识别肿瘤进展风险最高的患者。