21. Are industry-sponsored clinical trials cited more than

Are industry-sponsored clinical trials cited more than trials
sponsored by government, not-for-profits or academia?
A review of oncology journals at NPG
Neil Adams1, Jamie Feigenbaum1, Kathleen P. Lyons1, Pooja Aggarwal2, Martin Delahunty2
1Nature
Publishing Group, New York, USA,
2Nature
Publishing Group, London, UK
Abstract
Objectives
Results
Objective: It is widely accepted that clinical trials sponsored by
the pharmaceutical industry are cited more in scientific literature
than non-industry trials. One study showed that industrysponsored trials published in major general medical journals
were cited 1½ – 2 times more often than non-industry trials [1].
The authors state that their findings might not be generalizable to
other journals, however, because they did not examine specialty
journals. Our objective is to expand on these findings by
investigating citations in oncology journals published by NPG.
To expand on the findings of Lundh et al. (2010), this
study aims to investigate the relationship between
funding source and number of citations of clinical trials
published within the specialty area of Oncology.
Table 1. Mann-Whitney U test analysis for All Journals (pooled
citation data across titles) including all 1,426 articles.
Research Design: We analyzed clinical trials published in British
Journal of Cancer, Leukemia, Bone Marrow Transplantation and
Prostate Cancer and Prostatic Diseases from 2004-2011.
Sponsors were identified from the acknowledgement sections
and citation information was provided by Web of Science. We
excluded studies with mixed sponsorship and used a
Mann-Whitney U test for statistical significance.
By utilizing PubMed, Nature.com archives, and ISI Web
of Science citation data, this study is easily replicable for
other specialty areas and other publishing agencies.
Research Design
Minimum
1st Quartile
Median
3rd Quartile
Maximum
Non-Industry Industry
1190
236
Normal Approximation
z= 1.83398
Industry
Sponsored
0
8
18
35.25
406
U
151018.5
Non-Industry
Sponsored
0
7
15
29
187
P (two-tailed)
0.066084
P (one-tailed)
0.033042
0.666576
0.333288
Figure 1. Average Number of Citations Received By Clinical
Trials as shown by Funding Sponsor Type and Journal Title.
60
50
Results: An analysis of 1,426 papers revealed that citations from
industry-sponsored trials were higher than non-industry trials in
all groups [1st Quartile (8,7); Median (18,15); 3rd Quartile
(35.25,29); Maximum (406,187)] except Minimum (0,0).
P-value (two-tailed) was approximately 0.066084.
40
30
Indusrty
Non-Industry
20
Conclusion: Industry-sponsored clinical trials were cited more
often than non-industry trials for these specialized journals.
However, citation results varied greatly within and across titles.
10
0
British Journal of
Cancer
Keywords: Journals, Metrics, Industry
Leukemia
Bone Marrow
Transplantation
Prostate Cancer and
Prostatic Diseases
Figure 2. Box Plot Comparing the Number of Citations Journals
Received By Article Funding Type
Introduction
Industry-supported clinical trials receive more citations than other
types of clinical trials. Reasons for this are three-fold:
1) Industry-supported trials that get published are often
large and involve drug interventions, which have been
found to correlate with increased numbers of citations [2,3]
2) Published industry-supported trials are more likely to have
positive results compared to non-industry trials [4],
and positive industry trials receive more citations than
negative ones [2,3]
3) Industry has the means to promote and disseminate
published studies through marketing and reprint
distribution, which leads to increased awareness for their
findings, which can lead to more citations.
A 2010 study by Lundh, Barbateskovic, Hróbjartsson and
Gøtzsche aimed to determine the relative influence that citations
from industry-supported clinical trials had on the impact factors of
six major medical journals (Annals of Internal Medicine, Archives
of Internal Medicine, BMJ, JAMA, The Lancet, and New England
Journal of Medicine) over the course of a decade. These
researchers looked at the funding sources (Industry supported,
Non-industry supported, and Mixed support) and number of
citations of 1,353 clinical trials published in these titles in
1996–1997 and 2005–2006 to determine the influence that
citations to industry-sponsored studies had on the journals’
impact factors over time. In all cases, industry-supported trials
boosted the approximate impact factor for all six journals, with
some degree of variation—the most for NEJM and the least
for BMJ. It also showed that industry-sponsored trials published
in these major general medical journals were cited 1½ – 2 times
more often than non-industry trials [1].
The study by Lundh et al. (2010) only looked at the relationship
between clinical trial funding and number of citations for journals
from the ISI Web of Science Category of
“Medicine, General & Internal,” which the authors acknowledged
was very broad, and thus, a limitation. By looking at specialty
journals from the subject area of Oncology, our study builds on
and expands the scope of past research, as well as investigates
the degree to which industry-sponsored trials receive more
citations than non-industry supported trials in a specific area of
medical research.
1. Four Oncology journals published by Nature Publishing
Group (NPG) were selected based on the size of their
archive and their frequent publication of clinical trials.
2. To make this study replicable, a PubMed search of each
title was used to identify content published between
2004 and 2011.
3. Results were narrowed down to only those article types
identified as Clinical Trials. This allowed for comparison
to past research.
4. We identified the financial sponsors of each article from the
Acknowledgements section on the digital versions of the
clinical trials found in the Nature.com archives.
Each article was identified by funding type:
• Industry Sponsored
• Non-Industry Sponsored
• Mixed Sponsorship
As the term “Mixed Sponsorship” raised too many questions
about funding balances, these articles were removed from
the study.
5. The number of citations each article received was
determined using Web of Science.
6. A Mann-Whitney U test was run to examine statistical
significance between funding source and number of citations
for these clinical trials.
References
1. Lundh A, Barbateskovic M, Hróbjartsson A, Gøtzsche PC (2010) Conflicts of Interest at
Medical Journals: The Influence of Industry-Supported Randomised Trials on Journal Impact
Factors and Revenue – Cohort Study. PLoS Med 7(10): e1000354.
2. Kulkarni AV, Busse JW, Shams I (2007) Characteristics associated with citation rate of the
medical literature. PLoS ONE 2: e403.
3. Conen D, Torres J, Ridker PM (2008) Differential citation rates of major cardiovascular
clinical trials according to source of funding: a survey from 2000 to 2005. Circulation 118:
1321–1327.
4. Lexchin J, Bero LA, Djulbegovic B, Clark O (2003) Pharmaceutical industry sponsorship and
research outcome and quality: systematic review. BMJ 326: 1167–1170.
Conclusions
Industry-sponsored clinical trials received more citations in total
and on average than non-industry trials for specialized Oncology
journals at NPG, but citation results varied greatly across titles,
and the results of the Mann-Whitney U Test were not statistically
significant for this sample [P-value (two-tailed) was
approximately 0.066084]. These findings fit with the conclusions
found by Lundh et al. (2010), which also found that
industry-sponsored titles received more citations, but that
influence of funding type varied greatly between titles.
One limitation of this study is that the results are not
generalizable to journals in other specialties. Another limitation
has to do with the classification of funding source based on the
Acknowledgements section. Our assumption that trials with no
statement of industry support, or which only listed non-industry
support, were not supported by industry may have led to an
underestimation of industry-supported trials. Trials with mixed
sponsorship present an interesting area for future study. We
elected to disregard trials with mixed sponsorship in our study
(unlike Lundh et al.) because it is not possible to determine the
degree of support in each mixed case from the paper itself.
This area warrants further research, which includes review of
other specialties or a different cluster of journals within the
same specialty. Likewise, the relationship between funding type
and number of citations is important to investigate since
industry-supported studies with high numbers of citations can
greatly influence the impact factor of a journal.

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