To the Editor:
Three different publications in the July 7, 2016 issue of the Journal introduce the concept of adaptive clinical trials and state that, compared to classical “frequentist” trials, adaptive trials may require smaller groups of subjects and be completed more quickly (1) (2) (3). Yet, neither of the adaptive trials reported in the same issue (4) (5) described how long it took to recruit their subjects, nor estimated how long an equivalent classical trial might have required. Such comparisons would be of interest, as small reductions in time might not be worth the additional complexity that attends adaptive trials.
 Bhatt DL, Mehta C. The changing face of clinical trials: adaptive designs for clinical trials. N Engl J Med. 2016; 375: 65-74.
 Harrington D, Parmigiani G. Statistics in medicine: I-SPY 2 -- a glimpse of the future of phase 2 drug development? N Engl J Med. 2016; 375:7-9
 Carey LA, Winer EP. I-SPY 2 -- toward more rapid progress in breast cancer treatment. N Engl J Med. 2016; 375: 83-84.
 Park JW, et al. Adaptive randomization of neratinib in early breast cancer. N Engl J Med. 2016; 375: 11-22.
 Rugo HS, et al. Adaptive randomization of veliparib–carboplatin treatment in breast cancer. N Engl J Med. 2016; 375:23-34.