Intended for healthcare professionals

Rapid response to:

Education And Debate

Monitoring clinical trials—interim data should be publicly available

BMJ 2001; 323 doi: (Published 25 August 2001) Cite this as: BMJ 2001;323:441

Rapid Response:

Some reasons for caution in releasing interim trial data

Interpretation of trial data even at trial closure can sometimes be
controversial and difficult. Whilst there may be arguments in some cases
for releasing interim data, [1]depending on the type of trial and strength
of findings, there are surely also strong arguments for patient partipants
and trialists keeping their nerve until all results are gathered in? Why
else do we employ statisticians to undertake power calculations and
provide recommendations of cohort size needed to produce reliable data?
Visualisation of what recruitment by randomisation means has been
facilitated by likening it to the uneven and random distribution of
raindrops on a surface prior to complete coverage. It has also been my
understanding that both earlier trials in a series for review, and interim
results within a trial, can be misleading in the apparent direction of

Marketing pressure can also lead to premature stoppage of trials,
where profit rather patients may be the prime motivation for invoking
them, depriving not only "far term" but also "near term" participants of
the satisfaction of finding out the long term benefits and the overall
health benefits of an intervention already fully administered to many
"near term" participants. This was the case in the controversial stoppage
of the U.S. trial of Tamoxifen for the prevention of breast cancer. [2] It
is interesting that the European Prevention Trials did not follow suit,
perhaps because of a more convergent and sensitive motivation of trialist
with participant, and joint determination to obtain long-term data in
spite of apparent U.S. interim findings. [3]

If profession and patients collaborate in designing trials with
agreed long and short term objectives and aims, agreed stopping rules and
procedures for rapid and thorough dissemination of results, including both
professional and lay interpretations, we might all derive full benefit and
satisfaction from staying the course until the end. If patients are equal
partners in devising such contracts with professionals, by being on trial
steering committees and data monitoring committees, they will have equal
opportunity to make decisions about whether or not to abandon the trial,
or release interim data.

Many participants joint trials for altruistic reasons (23.1%) or
trust in the doctor (21.1%) a recent survey of cancer patients found - not
for what benefit they hope to get from it. [4] Why then adopt a shortcut
process that reduces the amount of learning, understanding and benefit
obtained from trials with participants who will have received an
intervention that cannot be undone?

Hazel Thornton.

Independent advocate for quality in research and healthcare.


[1] Richard J. Lilford, David Braunholz, Sarah Edwards, Andrew Stevens.
Monitoring clinical trials - interim data should be publicly available.
BMJ (2001) 323: 441-442.

[2] Fisher, B. Current controversies in cancer. Tamoxifen for the
prevention of breast cancer: pro. Eur. J.Cancer (2000) 36: 142-150

[3] Thornton, H. Relationship of trial design to value of data for
patient? Eur. J.Cancer (2000) 36: 1585-1586

[4] V. Jenkins and L. Fallowfield. Reasons for accepting or declining to
participate in randomised clinical trials for cancer therapy. British
Journal of Cancer (2000) 82(11); 1783-1788.

Competing interests: No competing interests

28 August 2001
Hazel Thornton
Honorary Visiting Fellow, Department of Epidemiology and Public Health, University of Leicester.
"Saionara", 31 Regent Street, Rowhedge, Colchester, CO5 7EA U.K.