On 2013 Jul 17, James Troendle commented:

The section on the importance of interim monitoring leaves out one important drawback to sequential studies when the sequential design is motivated by reducing the sample size. Yes, sequential studies can on average reduce the sample size. However, they do that by delivering reduced precision of the effect estimate. This reduction in precision of the final estimate is often ignored when a decision is made about whether to adopt a sequential or fixed design.

On 2013 Jul 17, James Troendle commented:

The section on the importance of interim monitoring leaves out one important drawback to sequential studies when the sequential design is motivated by reducing the sample size. Yes, sequential studies can on average reduce the sample size. However, they do that by delivering reduced precision of the effect estimate. This reduction in precision of the final estimate is often ignored when a decision is made about whether to adopt a sequential or fixed design.