On the Time to Conclusion of Phase II Cancer Clinical Trials and Its Application in Trial Designs
Most phase II cancer trials evaluate total response (TR) rate using a single-arm open-label design. Simon's two-stage design minimizes either the expected or the total number of patients. In this article, we investigate the distribution of time to reaching trial conclusion (TRTC) of such two-stage trials, which considers the accrual rate, time to TR, futility, and efficacy decision rules. We develop a Monte Carlo algorithm for the distribution of TRTC for both one- and two-stage phase II designs. We further propose an optimal design that balances the needs of concluding the trial within the required time period and minimizing the expected sample size. Generalized recursive formulas are derived analytically in the Appendix, which are theoretically interesting but not recommended for practical use. In conclusion, a consideration of the TRTC can lead to an optimal design with a minimum increase in the expected number of patients but an increased confidence in reaching study conclusions within the required time.