NPY Gene Methylation as a Universal, Longitudinal Plasma Marker for Evaluating the Clinical Benefit from Last-Line Treatment with Regorafenib in Metastatic Colorectal Cancer

There is a need for biomarkers to improve the clinical benefit from systemic treatment of colorectal cancer. We designed a prospective, clinical study where patients receiving regorafenibas last-line treatment had sequential blood samples drawn. Effect and toxicity was monitored. The primary clinical endpointwas progression free survival (PFS). Cell-free circulating tumor (ct) DNA was measured as either the fraction with Neuropeptide Y (NPY) methylated DNA or KRAS/NRAS/BRAF mutated ctDNA. One hundred patients were included from three Danish centers. Among 95 patients who received regorafenibfor at least two weeks, the medianPFS was 2.1 months (95% confidence interval (CI) 1.8–3.3) and the medianoverall survival (OS) was 5.2 months (95% CI 4.3–6.5). Grade 3–4 toxicities were reported 51 times, most frequently hypertension, hand-food syndrome, and skin rash. In the biomarker population of 91 patients, 49 could be monitored using mutated DNA and 90 using methylated DNA. There was a strong correlation between mutated and methylated DNA. The mediansurvival for patients with a level of methylated ctDNA above the medianwas 4.3 months compared to 7.6 months with ctDNA below the median, p < 0.001. The mediantime from increasing methylated ctDNA to disease progression was 1.64 months (range 0.46–8.38 months). In conclusion, NPY methylated ctDNA was a universal liquid biopsymarker in colorectal cancer patients treated with regorafenib. High baseline levels correlated with short survival and changes during treatment may predict early effectand later progression. We suggest plasma NPY methylation analysis as an easy and universally applicable method for longitudinal monitoring of ctDNA in metastatic colorectal cancer patients.