Pre-operative plasma cell-free circulating tumor DNA and serum protein tumor markers as predictors of lung adenocarcinoma recurrence

Background: Lung cancer patients have a risk of recurrence even after curatively intended surgery. Cell-free circulating tumor DNA (ctDNA) and circulating tumor marker measurements are easily accessible through peripheral blood and could potentially identify patients with worse prognosis. The aim of this study was to examine ctDNA in pre-operative plasma and the role of tumor markers in pre-operative serum for their predictive potential on risk of tumor recurrence.
Methods: Mutation analysis by 26-gene targeted sequencing was performed on 157 lung adenocarcinomas (ACs) from patients surgically treated at the Lund University Hospital 2005–2014. Of these, 58 tumors from patients in stages I–IIIA (34 stage I, 14 stage II and 10 stage III) with mutation(s) in EGFR, BRAF or KRAS were included. ctDNA from corresponding plasma (median 1.5 ml, range 1–1.6) was analyzed for one tumor-specific mutation in either of these three oncogenes using ultrasensitive IBSAFE droplet digital PCR (ddPCR). The tumor markers cancer antigen 125 (CA 125) and carbohydrate antigen 19-9 (CA 19-9) were analyzed in corresponding serum with electrochemiluminiscence immunoassay.
Results: 6/7 patients with ctDNA and 19/51 without detected ctDNA were diagnosed with recurrence (log-rank test p = .001). 8/10 patients with positive serum tumor markers and 17/47 without tumor markers were diagnosed with recurrence (log-rank test, p = .0002). Fifteen patients had positive ctDNA and/or tumor markers, 12 of these had recurrence (log-rank test, p < .0001).
Conclusion: A combination of tumor markers and ctDNA single mutation detection in low-volume pre-operative blood samples is a promising prognostic test. Prediction of recurrent disease in surgically treated early stage lung cancer can likely be further improved by using larger volumes of blood.

研究背景：肺癌患者即使接受了根治性手术，仍存在复发风险。游离循环肿瘤DNA（cell-free circulating tumor DNA, ctDNA）与循环肿瘤标志物可通过外周血便捷获取，或可用于识别预后不良的患者。本研究旨在检测术前血浆中的ctDNA，并探讨术前血清肿瘤标志物对肿瘤复发风险的预测价值。
研究方法：对2005年至2014年在隆德大学医院接受手术治疗的157例肺腺癌（AC）患者样本进行26基因靶向测序突变分析。其中，纳入了58例I~IIIA期（34例I期、14例II期、10例III期）且携带EGFR、BRAF或KRAS基因突变的患者肿瘤样本。对对应血浆（中位体积1.5ml，范围1~1.6ml）中的ctDNA，采用超灵敏IBSAFE液滴数字PCR（ddPCR）检测上述三种癌基因中任一肿瘤特异性突变。采用电化学发光免疫分析法检测对应血清中的肿瘤标志物癌抗原125（CA 125）与糖链抗原19-9（CA 19-9）。
研究结果：检出ctDNA的患者中6/7例确诊复发，未检出ctDNA的患者中19/51例确诊复发（对数秩检验，p=0.001）。血清肿瘤标志物阳性的患者中8/10例确诊复发，标志物阴性的患者中17/47例确诊复发（对数秩检验，p=0.0002）。共15例患者ctDNA阳性和/或肿瘤标志物阳性，其中12例出现复发（对数秩检验，p<0.0001）。
研究结论：术前小体积血液样本中肿瘤标志物与ctDNA单突变检测的联合应用，是一种极具前景的预后检测手段。若采用更大体积的血液样本，或可进一步提升手术治疗后早期肺癌患者复发风险的预测效能。