Abstract

Colorectal (CRC) and lung adenocarcinoma share many genetic and pathological similarities. A circulating tumor DNA (ctDNA) test for CRC may also be useful for detection of lung adenocarcinoma. This study determined if a methylated BCAT1/IKZF1 ctDNA test for CRC can be used for detection of lung adenocarcinoma. Circulating cell free DNA (ccfDNA) was extracted from plasma collected prospectively from healthy controls, patients in remission from CRC, patients with lung adenocarcinoma, and patients with isolated metastatic CRC lung lesions. Plasma ccfDNA was bisulfite converted and assessed for methylated BCAT1/IKZF1 by quantitative real-time PCR. Comparisons between the different patient groups for a positive ctDNA test (BCAT1 and/or IKZF1) and ctDNA levels (% of total ccfDNA), as well as any associations with clinicopathological and demographic features, were assessed. Methylated BCAT1/IKZF1 ctDNA was detected in 18/39 (46.2 %) patients with lung adenocarcinoma, which was significantly (p < 0.001) higher compared to healthy controls (49/606; 8.1 %) and patients in remission from CRC (22/171, 12.9 %). Patients with stage III/IV lung adenocarcinoma had higher BCAT1/IKZF1 ctDNA positivity compared to stage I/II cases (68.2 % vs 17.7 %, p < 0.01), where a significantly higher proportion tested positive for methylated IKZF1 ctDNA alone (54.6 % vs 5.9 %, p < 0.001). There was no difference in BCAT1/IKZF1 ctDNA test positivity between patients with stage IV primary lung adenocarcinoma (n = 17) compared to lung-metastasising CRC cases (n = 17; 70.6 % v 64.3 %). A ctDNA test measuring methylated BCAT1/IKZF1 can sensitively detect lung adenocarcinoma and may be a promising aid for detection of advanced disease. Australian and New Zealand Clinical Trials Registry, www.anzctr.org.au, ACTRN12616001138471, ACTRN12611000318987.