Context Large clinical trials are the criterion standard for making treatment
decisions, and nonpublication of the results of such trials can lead to bias
in the literature and contribute to inappropriate medical decisions.
Objectives To determine the rate of full publication of large randomized trials
presented at annual meetings of the American Society of Clinical Oncology
(ASCO), quantify bias against publishing nonsignificant results, and identify
factors associated with time to publication.
Design Survey of 510 abstracts from large (sample size, ≥200), phase 3,
randomized controlled trials presented at ASCO meetings between 1989 and 1998.
Trial results were classified as significant (P≤.05
for the primary outcome measure) or nonsignificant (P>.05
or not reported), and the type of presentation and sponsorship were identified.
Subsequent full publication was identified using a search of MEDLINE and EMBASE,
completed November 1, 2001; the search was updated in November 2002, using
the Cochrane Register of Controlled Trials. Authors were contacted if the
searches did not find evidence of publication.
Main Outcome Measures Publication rate at 5 years; time from presentation to full publication.
Results Of 510 randomized trials, 26% were not published in full within 5 years
after presentation at the meeting. Eighty-one percent of the studies with
significant results had been published by this time compared with 68% of the
studies with nonsignificant results (P<.001).
Studies with oral or plenary presentation were published sooner than those
not presented (P = .002), and studies with pharmaceutical
sponsorship were published sooner than studies with cooperative group sponsorship
or studies for which sponsorship was not specified (P =
.02). These factors remained significant in a multivariable model. The most
frequent reason cited by authors for not publishing was lack of time, funds,
or other resources.
Conclusions A substantial number of large phase 3 trials presented at an international
oncology meeting remain unpublished 5 years after presentation. Bias against
publishing nonsignificant results is a problem even for large randomized trials.
Nonpublication breaks the contract that investigators make with trial participants,
funding agencies, and ethics boards.