A Trial Protocol of Biweekly TAS-102 and Bevacizumab as Third-Line Chemotherapy for Advanced/Recurrent Colorectal Cancer: A Phase II Multicenter Clinical Trial (The TAS-CC4 Study)

Background: Treatment with TAS-102 has significantly improved the progression-free survival (PFS) and overall survival (OS) of patients with metastatic colorectal cancer (mCRC). Reportedly, the combination of TAS-102 plus bevacizumab extends the median PFS. The present study aimed to confirm the efficacy and safety of TAS-102 plus bevacizumab (biweekly administration) as third-line chemotherapy for patients with mCRC. Methods/Design: This is a single-arm, open-label, prospective, nonrandomized, multicenter phase II trial conducted in Japan. With a threshold and expected PFS of 2.1 and 3.5 months, respectively, the simulation results showed a sample size of 42 with α = 0.05 (both sides) for 90% power, based on the One-Arm Binomial test using the SWOG statistical tool. If the estimated dropout is 7%-8%, the target sample size is estimated to be 45. The TAS-CC4 study regimen comprised 28-day cycles with biweekly oral administration of TAS-102 (35 mg/m2 twice daily on days 1-5 and 15-19 of every 28-day cycle) and bevacizumab (5.0 mg/kg on days 1 and 15). The primary end point is the PFS; secondary end points include response rate (RR), OS, grade ≥3 neutropenia, and genetic alterations (KRAS/BRAF mutations) in the circulating cell-free DNA. Discussion: The present study can contribute to the determination of the effective dosing interval of TAS-102 and bevacizumab in patients with mCRC and is thought to lead to prophylaxis of neutropenia and prolongation of the treatment period.