A Single-Arm, Phase II Study of Apatinib in Refractory Metastatic Colorectal Cancer.

Background. Apatinib, an oral vascular endothelial growth factor (VEGF) receptor-2 inhibitor, has been approved as third-line treatment for metastatic gastric cancer in China. The aim of this study was to evaluate the efficacy and safety of apatinib, in the treatment of patients with refractory metastatic colorectal cancer after failure of two or more lines of chemotherapy. Methods In this open-label, single-arm, phase II study, patients with histological documentation of adenocarcinoma of the colon or rectum were eligible if they had received at least two prior regimens of standard therapies including fluoropyrimidine, oxaliplatin, and irinotecan. These patients were treated with apatinib in a daily dose of 500 mg, p.o., in the third-line or higher setting. Capture sequencing was dynamically performed to identify somatic variants in circulating tumor DNA (ctDNA) with a panel of 1,021 cancer-related genes. The primary endpoint was progression-free survival (PFS) and the tumor response was determined according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Interim analysis was applied as predefined. Results From June 1, 2016 to December 31, 2017, 26 patients were enrolled. The median PFS of the whole group was 3.9 months (95% confidence interval [CI]: 2.1-5.9). The median overall survival (OS) was 7.9 months (95% CI: 4.6-10.1+). Patients with performance status (PS) 0-1 had longer PFS than those with PS 2 (4.17 months vs. 1.93 months, p = .0014). Patients without liver metastasis also had longer PFS than those who had live metastasis (5.87 months vs. 3.33 months, p = .0274). The common side effects of apatinib were hypertension, hand-foot syndrome, proteinuria, and diarrhea. The incidence of grade 3-4 hypertension, hand-foot syndrome, proteinuria, and diarrhea was 76.92%, 11.54%, 73.08%, and 23.08%, respectively. All of the patients received dose reduction because of adverse effect. Results of capture sequencing showed APC, TP53, and KRAS were most frequently mutant genes. ctDNA abundance increased before the radiographic assessment in ten patients. Conclusion Apatinib monotherapy showed promising efficiency for patients with refractory colorectal cancer, especially in patients with PS 0-1 or no liver metastasis. ctDNA abundance may be a predictor in serial monitoring of tumor load.