Assessing the Eventual Publication of Clinical Trial Abstracts Submitted to a Large Annual Oncology Meeting (ASCO)

  Materials and Methods. Abstracts describing clinical trials for
patients with breast, lung, colorectal, ovarian, and prostate
cancer from 2009 to 2011 were identified by using a
comprehensive online database (http://meetinglibrary.asco.
org/abstracts).....

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Background.

Despite the ethical imperative to publish clinical trials when human subjects are involved, such data frequently remain unpublished. The objectives were to tabulate the rate and ascertain factors associated with eventual publication of clinical trial results reported as abstracts in the Proceedings of the American Society of Clinical Oncology (American Society of Clinical Oncology).

Materials and Methods.

Abstracts describing clinical trials for patients with breast, lung, colorectal, ovarian, and prostate cancer from 2009 to 2011 were identified by using a comprehensive online database (http://meetinglibrary.asco.org/abstracts). Abstracts included reported results of a treatment or intervention assessed in a discrete, prospective clinical trial. Publication status at 4−6 years was determined by using a standardized search of PubMed. Primary outcomes were the rate of publication for abstracts of randomized and nonrandomized clinical trials. Secondary outcomes included factors influencing the publication of results.

Results.

A total of 1,075 abstracts describing 378 randomized and 697 nonrandomized clinical trials were evaluated. Across all years, 75% of randomized and 54% of nonrandomized trials were published, with an overall publication rate of 61%.

Sample size was a statistically significant predictor of publication for both randomized and nonrandomized trials (odds ratio [OR] per increase of 100 participants = 1.23 [1.11–1.36], p < .001; and 1.64 [1.15–2.34], p = .006, respectively). Among randomized studies, an industry coauthor or involvement of a cooperative group increased the likelihood of publication (OR 2.37, p = .013; and 2.21, p = .01, respectively). Among nonrandomized studies, phase II trials were more likely to be published than phase I (p < .001). Use of an experimental agent was not a predictor of publication in randomized (OR 0.76 [0.38–1.52]; p = .441) or nonrandomized trials (OR 0.89 [0.61–1.29]; p = .532).

Conclusion.

This is the largest reported study examining why oncology trials are not published. The data show that 4−6 years after appearing as abstracts, 39% of oncology clinical trials remain unpublished. Larger sample size and advanced trial phase were associated with eventual publication; among randomized trials, an industry-affiliated author or a cooperative group increased likelihood of publication. Unfortunately, we found that, despite widespread recognition of the problem and the creation of central data repositories, timely publishing of oncology clinical trials results remains unsatisfactory.

Implications for Practice:

The Declaration of Helsinki Ethical Principles for Medical Research Involving Human Subjects notes the ethical obligation to report clinical trial data, whether positive or negative. This obligation is listed alongside requirements for risk minimization, access, confidentiality, and informed consent, all bedrocks of the clinical trial system. Yet clinical trials are often not published, particularly if negative or difficult to complete. This study found that among American Society for Clinical Oncology (ASCO) Annual Meeting abstracts, 2009–2011, only 61% were published 4–6 years later: 75% of randomized trials and 54% of nonrandomized trials. Clinicians need to insist that every study in which they participate is published.