Purpose

This study aimed to investigate factors, which influence the content of circulating tumor DNA (ctDNA).

Methods

398 serial plasma samples were collected within 1–7 consecutive days from patients with EGFR-mutated lung cancer (n = 13), RAS/RAF-mutated colorectal cancer (n = 54) and BRAF-mutated melanoma (n = 17), who presented with measurable tumor disease. The amount of ctDNA was determined by ddPCR.

Results

Among 82 patients, who donated 2–6 serial plasma samples, 42 subjects were classified as ctDNA-positive; only 22% cases were mutation-positive across all consecutive tests, while 24/82 (29%) patients showed presence of mutated ctDNA in some but not all blood draws. Subjects with progressing tumors had higher probability of being detected ctDNA-positive as compared to patients, who responded to therapy or had stable disease (39/55 (71%) vs. 4/24 (17%); p = 0.0001). Our study failed to reveal the impact of the time of the day, recent meal or prior physical exercise on the results of ctDNA testing.

Conclusions

Presence of ctDNA in plasma is particularly characteristic for patients, who experience clinical progression of tumor disease. Consecutive plasma tests may occasionally provide discordant data; thus, the repetition of analysis may be advised in certain cases in order to ensure the validity of negative ctDNA result.

中文翻译：

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循环肿瘤 DNA 的含量取决于肿瘤类型和肿瘤大小的动态，但不受体育锻炼、一天中的时间或最近的饮食的显着影响

目的

本研究旨在调查影响循环肿瘤 DNA (ctDNA) 含量的因素。

方法

在连续 1-7 天内从EGFR突变的肺癌（n  = 13）、RAS/RAF突变的结直肠癌（n  = 54）和BRAF突变的黑色素瘤（n  = 17）患者中收集了 398 个系列血浆样本，他们出现可测量的肿瘤疾病。通过ddPCR确定ctDNA的量。

结果

在捐赠了 2-6 个连续血浆样本的 82 名患者中，42 名受试者被归类为 ctDNA 阳性；在所有连续测试中，只有 22% 的病例为突变阳性，而 24/82 (29%) 的患者在一些但并非所有抽血中显示出突变的 ctDNA。与对治疗有反应或疾病稳定的患者相比，患有进展性肿瘤的受试者被检测到 ctDNA 阳性的可能性更高（39/55（71%）对 4/24（17%）；p  = 0.0001）。我们的研究未能揭示一天中的时间、最近进餐或之前的体育锻炼对 ctDNA 检测结果的影响。

结论

对于经历肿瘤疾病临床进展的患者而言，血浆中 ctDNA 的存在尤其具有特征性。连续的血浆测试有时可能会提供不一致的数据；因此，在某些情况下可能会建议重复分析，以确保阴性 ctDNA 结果的有效性。