Patient-Oriented Cancer Information on the Internet: A Comparison of Wikipedia and a Professionally Maintained Database
A wiki is a collaborative Web site, such as Wikipedia, that can be freely edited. Because of a wiki's lack of formal editorial control, we hypothesized that the content would be less complete and accurate than that of a professional peer-reviewed Web site. In this study, the coverage, accuracy, and readability of cancer information on Wikipedia were compared with those of the patient-orientated National Cancer Institute's Physician Data Query (PDQ) comprehensive cancer database. For each of 10 cancer types, medically trained personnel scored PDQ and Wikipedia articles for accuracy and presentation of controversies by using an appraisal form. Reliability was assessed by using interobserver variability and test-retest reproducibility. Readability was calculated from word and sentence length. Evaluators were able to rapidly assess articles (18 minutes/article), with a test-retest reliability of 0.71 and interobserver variability of 0.53. For both Web sites, inaccuracies were rare, less than 2% of information examined. PDQ was significantly more readable than Wikipedia: Flesch-Kincaid grade level 9.6 versus 14.1. There was no difference in depth of coverage between PDQ and Wikipedia (29.9, 34.2, respectively; maximum possible score 72). Controversial aspects of cancer care were relatively poorly discussed in both resources (2.9 and 6.1 for PDQ and Wikipedia, respectively, NS; maximum possible score 18). A planned subanalysis comparing common and uncommon cancers demonstrated no difference. Although the wiki resource had similar accuracy and depth as the professionally edited database, it was significantly less readable. Further research is required to assess how this influences patients' understanding and retention.
Patient-Oriented Cancer Information on the Internet:
A Comparison of Wikipedia and a Professionally
By Malolan S. Rajagopalan, MD, Vineet K. Khanna, MD, Yaacov Leiter, MS, MD, Meghan Stott, MD,
Timothy N. Showalter, MD, Adam P. Dicker, MD, PhD, and Yaacov R. Lawrence, MA, MBBS, MRCP
Department of Radiation Oncology, University of Pittsburgh Cancer Institute; University of Pittsburgh School of Medicine,
Pittsburgh; Drexel University College of Medicine; Department of Radiation Oncology, Jefferson Medical College of Thomas
Jefferson University, Kimmel Cancer Center, Philadelphia, PA; Bruce and Ruth Rappaport Faculty of Medicine, Technion-Israel
Institute of Technology, Haifa, Israel
Purpose: A wiki is a collaborative Web site, such as Wikipedia,
that can be freely edited. Because of a wiki’s lack of formal
editorial control, we hypothesized that the content would be less
complete and accurate than that of a professional peer-reviewed
Web site. In this study, the coverage, accuracy, and readability of
cancer information on Wikipedia were compared with those of
the patient-orientated National Cancer Institute’s Physician Data
Query (PDQ) comprehensive cancer database.
Methods: For each of 10 cancer types, medically trained per-
sonnel scored PDQ and Wikipedia articles for accuracy and pre-
sentation of controversies by using an appraisal form. Reliability
was assessed by using interobserver variability and test-retest
reproducibility. Readability was calculated from word and sen-
Results: Evaluators were able to rapidly assess articles (18
minutes/article), with a test-retest reliability of 0.71 and interob-
server variability of 0.53. For both Web sites, inaccuracies were
rare, less than 2% of information examined. PDQ was signiﬁ-
cantly more readable than Wikipedia: Flesch-Kincaid grade level
9.6 versus 14.1. There was no difference in depth of coverage
between PDQ and Wikipedia (29.9, 34.2, respectively; maximum
possible score 72). Controversial aspects of cancer care were
relatively poorly discussed in both resources (2.9 and 6.1 for
PDQ and Wikipedia, respectively, NS; maximum possible score
18). A planned subanalysis comparing common and uncommon
cancers demonstrated no difference.
Conclusion: Although the wiki resource had similar accuracy
and depth as the professionally edited database, it was signiﬁ-
cantly less readable. Further research is required to assess how
this inﬂuences patients’ understanding and retention.
Over the past decade, the Internet has become an important
source of cancer information. At one cancer center in the
United States, 80% of patients had access to the Internet and
63% searched for cancer information online.
have been described in other medical specialties.
A decade ago, most Web sites were static; users passively
viewed content but were unable to create or share their own
ideas and knowledge. More recently, Web sites and online com-
munities have adopted a user-centric design that encourages
collaboration and personal interaction, an approach described
by the term “Web 2.0.”
Examples of Web 2.0 Web sites in-
clude online blogs, social networking sites (eg, Facebook) and
wikis. A wiki is a Web site that allows its users to edit its pages
online, creating and modifying the information that is publi-
cally available. Among wikis, Wikipedia (www.wikipedia.org),
an online collaborative encyclopedia, has achieved enormous
popularity and has become one of the world’s most trafﬁcked
Web sites, with more than 3 million English-language articles.
The freely editable nature of Wikipedia enables contribu-
tors, lay or expert, across the world to share their knowledge
easily. In addition, the content on the Web site can change
constantly and quickly to reﬂect the latest news and data, a
feature difﬁcult to implement in a formally edited encyclope-
Unfortunately, such a system can also propagate misinfor-
mation if users contribute erroneous data either accidentally or
maliciously. Although some such examples have become noto-
rious, they appear to be uncommon.
Because there is no formal
editing process, such errors will be corrected only if they are
recognized and deleted by other users.
The quality and accuracy of medical content available online
is a matter of concern. In particular, are user-edited wikis pro-
viding accurate, balanced, comprehensive information to pa-
tients and the wider community? We were especially concerned
that wikis may misconstrue nonscientiﬁcally proven beliefs as
fact or contain outright mistakes. Conversely, we hypothesized
that the wiki platform may be more conducive to a discussion of
controversial aspects of cancer care. To address these issues, we
compared the cancer information available on Wikipedia with
that of a more traditional online source, the patient-oriented
Physician Data Query (PDQ; www.cancer.gov/cancertopics/
pdq) maintained by the National Cancer Institute (NCI). The
PDQ is a series of professionally edited and maintained articles
that serve to educate patients with cancer about their disease. In
contrast to Wikipedia, the PDQ is not available for online
editing or modiﬁcation. It is produced by editorial boards com-
posed of oncologists, psychologists, geneticists, epidemiolo-
gists, and complementary medical practitioners according to a
rigid process that includes data gathering, writing, and editing.
This study sought to compare these two resources across a variety
SEPTEMBER 2011 • jop.ascopubs.org 319Copyright © 2011 by American Society of Clinical Oncology
of domains, including accuracy of content, depth of coverage of
topics, presentation of controversial issues in care, and readability.
Overall Study Design
Appraisal forms assessing the depth and accuracy of informa-
tion and the presentation of controversies were produced for
each cancer type. In order to ensure that all evaluators were
using the same text, PDFs were created from the PDQ articles
and Wikipedia articles as they appeared on August 26, 2009. In
cases where there were hyperlinks to highly relevant subarticles,
these were included as well. For the PDQ resource, these links
included prevention and screening articles. For Wikipedia, ma-
jor linked subheadings (represented on the parent article as “see
also”) were provided to the evaluators. These included articles
on staging, screening, and epidemiology, among others, and
varied on the basis of cancer type. The evaluators were in-
structed to score only the material presented to them in PDF
format, and not to consult with the Internet.
Five of the most common cancers and ﬁve of the less common
cancers were chosen on the basis of statistics published by
American Cancer Society.
The common cancer types were
lung, breast, prostate, colon, and melanoma, which have an
annual incidence in the United States ranging from 68,720 to
219,440. The less common cancer types were anal, vulvar, small
intestine, testicular, and osteosarcoma; these cancer sites have
an annual incidence ranging from 2,570 to 8,400.
Assessment of Accuracy and Depth of Coverage
For each cancer type, the study designers (M.S.R., Y.R.L.) assem-
bled an appraisal form that contained eight information statements
obtained from Abeloff’s Clinical Oncology textbook
in Devita’s Principles and Practice of Oncology.
ments, which were likely to be of interest and relevance to patients,
were chosen, encompassing the domains of epidemiology, etiol-
ogy, symptoms, diagnosis, and treatment. Evaluators were in-
structed to compare each information statement with the content
in the Wikipedia and PDQ PDFs and score the accuracy of the
information presented. The scoring system was as follows: 0 points
if the topic was not discussed, 1 point if there was a discussion of
the topic but with major omissions, 2 points if there was discussion
of the topic with only minor omissions, and 3 points if there was a
complete discussion of the topic; –1 point was scored if the content
in the resource was discordant with the information statement. In
addition, we examined the incidence of errors. An error was re-
corded only when two or more evaluators agreed that a Web site
presented a particular piece of information that was discordant
with the appraisal form.
Assessment of Controversial Aspects of Care
Two controversial topics for each cancer type were assessed.
These topics were chosen on the basis of a literature search using
the terms “disputed,” “controversial,” or “disagreement.” The
scoring system was as follows: 0 points if the topic was not
mentioned, 1 point if the topic was raised but the controversial
aspect was avoided, 2 points if the controversy was brieﬂy dis-
cussed, and 3 points for complete discussion of the controversy.
One month after completion of the study, in order to assess
the test-retest reliability, we asked all the evaluators to re-eval-
uate both the PDQ and Wikipedia articles for one cancer site,
using the same PDFs previously used. At the conclusion of the
assignment, evaluators were questioned regarding the time
needed to assess each web resource and to provide additional
feedback and criticism.
Assessment of Readability
Readability was calculated by using the validated Flesch-Kin-
caid grade level, which factors both word choice (number of
letters per word) and sentence structure (number of words per
For each article, three passages of text ranging be-
tween 90 and 120 words in length were randomly selected from
the beginning, middle, and end. This text was edited to remove
any citations, titles, headings, and references so as not to artiﬁ-
cially alter the calculated grade level. The Flesch-Kincaid grade
level was calculated by using Word 2007 (Microsoft, Red-
mond, WA), and the average readability score for each article
Assessment of References
For each article, the number of references was noted. In addi-
tion, each reference was categorized into one of the following
groups: academic journals, books, professional organizations,
news media (print or web), commercial (including pharmaceutical
companies), and other. A subanalysis comparing these results be-
tween common and uncommon cancers was also performed.
Frequency of Revisions to Wikipedia Articles
The Wikipedia Web site documents each time a particular ar-
ticle is changed or edited by its users. For the 10 cancer types
analyzed, we counted the number of edits over the course of the
year preceding this study (August 27, 2008 through August 26,
2009). The number of edits was averaged, and comparisons
between common and uncommon cancers were performed.
The ability of the Web sites to integrate new information was
compared by assessing whether they contained the results of
recently published clinical trials. We noted whether the relevant
Web sites referred to the results of the 10 most recent clinical
trial manuscripts of solid tumors in adults published in the New
England Journal of Medicine (April 2011 to February 2011).
This assessment was performed in mid-February 2011.
Comparisons between the Web sites were made by means of a
paired two-sided t test, with signiﬁcance set at P ⬍ .05. Reliability
was assessed by using interobserver variability (correlation coefﬁ-
cient) and test-retest reproducibility (Ebel’s algorithm).
Rajagopalan et alRajagopalan et al
320 JOURNAL OF ONCOLOGY PRACTICE •VOL.7,ISSUE 5 Copyright © 2011 by American Society of Clinical Oncology
Descriptive Comparison of the Two Resources
Wikipedia is an online collaborative encyclopedia that relies on
millions of users to create and edit its articles. With a staff of
only 35, the Wikimedia Foundation that oversees Wikipedia
has no role in content oversight. Articles are updated at any time
by any of its users. In contrast, the NCI PDQ has an editorial
board composed of experts in the ﬁelds of medical, radiation,
and surgical oncology. The editorial board reviews published
research studies on a monthly basis and meets eight times each
year to consider new information to integrate into the articles.
Both resources have a fairly consistent organizational scheme
for articles. Wikipedia articles begin with a short introduction
followed by a table of contents. Most articles then include sec-
tions on signs and symptoms, causes, pathogenesis, diagnosis,
screening, treatment, and prognosis. Articles concerning un-
common cancers lacked some sections; conversely, articles
about common cancers often included additional sections such
as history, prevention, and details of staging. All Wikipedia
articles contain external links and references (clearly annotated
in the text). PDQ articles were found to have the following
sections: general information (including overview, risk factors,
signs/symptoms, diagnosis), staging, and treatment options.
Separate articles on prevention and screening are also included.
Neither external links nor references are provided.
Recent changes to both resources are documented. The
PDQ includes a last-modiﬁed date along with a short sentence
describing the nature of the changes. In contrast, Wikipedia
articles have a link detailing every change made to the docu-
ment since its creation.
Overview of Reviewers
Evaluators required an average of 18 minutes to assess each article.
Test-retest reliability (1 month later) was calculated to be 0.71.
Using Ebel’s algorithm, the interobserver variability was found to
be 0.53 (a value of 1.00 would indicate perfect reliability).
Depth and Accuracy of Content
The maximum possible score for content for each resource was
72. There was no difference in the combined depth and accu-
racy of content between the Web sites (29.9 ⫾ 8.3 standard
deviation [SD], 34.2 ⫾ 14.0 SD for PDQ and Wikipedia,
respectively) (Figure 1). Errors were found to be rare in both
resources. Of the 80 information statements presented, there
were zero errors in PDQ articles and one in Wikipedia (0% v
Coverage of Controversial Aspects of Care Was Not
Different Between the Resources
The maximum possible score for complete coverage of contro-
versial aspects averaged across the 10 disease sites was 18. Con-
troversial aspects of cancer care were poorly discussed in both
resources (2.9 ⫾ 2.8 SD and 6.1 ⫾ 6.3 SD for PDQ and
Wikipedia, respectively; NS) (Figure 2).
PDQ articles were found to be signiﬁcantly more readable than
those on Wikipedia, with a grade level of 9.6 ⫾ 1.5 SD versus
14.1 ⫾ 0.5 SD (P ⬍ .001) (Figure 3). This difference in grade
level between PDQ and Wikipedia was preserved when analyz-
ing common cancers (8.5 ⫾ 1.2 SD v 13.9 ⫾ 0.4 SD, P ⬍ .001)
and uncommon cancers (10.7 ⫾ 0.9 SD v 14.3 ⫾ 0.6 SD, P ⬍
In addition to this disparity in crude readability, we were
concerned that there might be an additional difference regard-
ing the use and explanation of technical words. Both Web sites
make extensive use of hypertext links, with multiple links per
paragraph. An important distinction is that whereas the PDQ
hypertext linked to a dictionary written in plain English, the
Wikipedia hypertext most often linked to highly technical articles.
Common cancers had signiﬁcantly more citations than uncom-
mon cancers (98.6 ⫾ 33.9 SD v 10.0 ⫾ 6.5 SD; P ⫽ .0036).
Depth and Accuracy Score
(max. score = 72)
P = NS
Figure 1. Depth and accuracy of content. Information statements ob-
tained from professional oncology texts were compared against con-
tent from both electronic resources and scored. max., maximum; PDQ,
Physician Data Query.
P = NS
Controversies Coverage Score
(max. score = 18)
Figure 2. Coverage of controversial topics. Topics of controversy or
debate were generated for each cancer site as described in the Meth-
ods section and were compared between the electronic resources.
max., maximum; PDQ, Physician Data Query.
Comparison of Cancer Information Online: Wikipedia and NCI PDQComparison of Cancer Information Online: Wikipedia and NCI PDQ
SEPTEMBER 2011 • jop.ascopubs.org 321Copyright © 2011 by American Society of Clinical Oncology
Common cancer articles were found to have a signiﬁcantly
higher percentage of Medline citations (62.2% v 24.2%; P ⫽
.037) and a lower percentage of citations from nonproﬁt orga-
nization or foundation Web sites (20.7% v 48.7%; P ⫽ .020).
No differences were detected in percentage of citations from
books, news media, commercial, and other (Appendix Figure
A1, online only). The patient-oriented PDQ does not include
Frequency of Revisions to Wikipedia Articles
We compared the frequency of revisions to Wikipedia articles
about common cancers with those about uncommon cancers
(Appendix Figure A2, online only). Articles about uncommon
cancers were edited signiﬁcantly less frequently than those
about common cancers (115.4 ⫾ 113.2 SD v 513.8 ⫾ 216.9
SD; P ⫽ .011).
Feedback obtained at the conclusion of the study revealed that
appraisal of an article required an average of 18 minutes. In
addition, the evaluators were asked to rate the fairness of the
appraisal form on a scale of 1 to 5 (with 5 representing the most
fair); average score was 4.7.
A study was performed to assess the integration of current data
within each resource. Out of a maximal possible score of 10,
Wikipedia scored 4 and PDQ 0 (P ⬍ .04).
In order to put our results in context, we investigated which
Web site was favored by popular search engines. A variety of
cancers were searched for by using both Google (www.google.
com) and Bing (www.bing.com). Both Wikipedia and PDQ
links typically appeared within the top 10 search results. In
more than 80% of cases, Wikipedia appeared above PDQ in the
Patients and their families are increasingly turning to the Web
as a source of medical information.
In the last several years,
there has been a tremendous growth in collaborative, Web 2.0
sites such as the online public encyclopedia Wikipedia, which
enables any visitor to contribute and edit any article (although
certain politically sensitive articles are not amenable to open
editing, this does not apply to cancer-related information). In
this study, we sought to determine how Wikipedia articles
about ﬁve common and ﬁve uncommon cancers compared with
articles about the same cancers from a peer-reviewed, expert-
generated Web site, NCI’s PDQ. The domains used for this
comparison included depth of content, accuracy, discussion of
controversial topics, and readability. In addition, the type and
quality of references cited in Wikipedia articles, as well as the
frequency with which these articles were edited, was assessed.
We found that although Wikipedia had similar accuracy and
depth to the PDQ, the written style was more complex and thus
might be less understandable to patients. We found no differ-
ence in the discussion of controversial topics between the two
resources. Although the Wikipedia articles appeared to be more
up-to-date, we acknowledge that this may possibly reﬂect a
policy of PDQ not to discuss published studies until the phar-
maceutical agents have been approved by the US Food and
Drug Administration. Finally, regarding references in Wikipe-
dia, more common cancer types had signiﬁcantly more cita-
tions, as well as a higher proportion of citations from Medline-
To our knowledge, this is the most comprehensive and rig-
orous study comparing oncology articles between an expert-
generated Web site and a wiki. Many parameters that are
directly relevant to a patient’s perspective, including accuracy,
depth, and readability, were assessed. Weaknesses of the study
include that its scope was limited to ﬁve common and ﬁve
uncommon cancers, the fact that only a limited number of Web
sites were examined, and the use of medically trained evaluators.
In future studies, we intend to use a larger number of evaluators
who are more representative of the general population.
Studies such as this one that assess the quality of online
content will be ever more important as the Internet continues to
increase in inﬂuence.
Wikipedia is an especially prominent
Web site; on general online searches for various medical terms
and diseases, Wikipedia articles ranked among the ﬁrst 10 re-
sults for 71% to 85% of the search engines and key words
tested, surpassing professionally maintained Web sites (eg, Na-
tional Institutes of Health MedlinePlus and National Health
Service Direct Online).
There have been very few studies
assessing the quality of Wikipedia’s medical articles. One study
that focused on osteosarcoma found that Wikipedia was infe-
rior to the NCI Web site.
Another study that assessed the
description of surgical procedures by Wikipedia found that al-
though all the entries presented accurate content, 37.1% of
articles had at least one critical omission. Interestingly, the
study found a positive correlation between the frequency with
which an article was edited and its accuracy.
The latter ﬁnding
partially concurs with our ﬁnding that articles about more com-
P < .001
Flesch-Kincaid Grade Level
Figure 3. Readability. Readability was assessed by using the Flesch-
Kincaid grade level, factoring word length and sentence structure. PDQ,
Physician Data Query.
Rajagopalan et alRajagopalan et al
322 JOURNAL OF ONCOLOGY PRACTICE •VOL.7,ISSUE 5 Copyright © 2011 by American Society of Clinical Oncology
mon cancer types, which were signiﬁcantly more frequently
edited, had better quality references than those about uncom-
Our data indicate that although the informational content
of articles on Wikipedia and PDQ is comparable, the former are
less easy to read. The hypertext links provided by PDQ to a lay
language dictionary further promote understanding, although
this was not formally assessed in the readability metric. The
implications of this disparity in reading grade are not known.
Several studies have concluded that those patients who look for
information online have above-average educations.
ever, many patients with cancer have impaired cognitive func-
A complete understanding of the impact of disease,
treatment, and educational attainment on the understanding
and retention of Web-based information, although important,
was beyond the scope of this study.
In conclusion, we found that Wikipedia and PDQ entries
have comparable depth and accuracy, but the former were sig-
niﬁcantly less readable. On the basis of the sample articles
tested, both appear to be reliable sources of information, but the
editorial processes used by PDQ created a more readable result.
Further research is required to ascertain what patient- and Web
page–related factors determine optimal understanding and ab-
sorption of information. Such research will help in the design of
the next generation of Web-based information systems.
Accepted for publication on March 24, 2011.
The Kimmel Cancer Center (A.P.D., Y.R.L., T.S.) is supported by Na-
tional Cancer Institute Grant No. 2 P30 CA056036-09. Y.R.L. is sup-
ported by a Young Investigator Award from the American Society for
Presented in part at the 46th Annual Meeting of the American Society of
Clinical Oncology, June 4-8, 2010.
Authors’ Disclosures of Potential Conﬂicts of Interest
The authors indicated no potential conﬂicts of interest.
Conception and design: Malolan S. Rajagopalan, Adam P. Dicker,
Yaacov R. Lawrence
Administrative support: Malolan S. Rajagopalan, Adam P. Dicker,
Yaacov R. Lawrence
Provision of study materials or patients: Malolan S. Rajagopalan,
Timothy N. Showalter
Collection and assembly of data: Malolan S. Rajagopalan, Vineet K.
Khanna, Yaacov Leiter, Meghan Stott, Timothy N. Showalter, Yaacov
Data analysis and interpretation: Malolan S. Rajagopalan, Vineet K.
Khanna, Yaacov Leiter, Adam P. Dicker, Yaacov R. Lawrence
Manuscript writing: Malolan S. Rajagopalan, Vineet K. Khanna,
Yaacov Leiter, Adam P. Dicker, Yaacov R. Lawrence
Final approval of manuscript: Malolan S. Rajagopalan, Vineet K.
Khanna, Yaacov Leiter, Meghan Stott, Timothy N. Showalter, Adam P.
Dicker, Yaacov R. Lawrence
Corresponding author: Yaacov R. Lawrence, MBA, MBBS, MRCP, De-
partment of Radiation Oncology, Sheba Medical Center, Tel HaShomer
52621, Israel; e-mail: email@example.com.
DOI: 10.1200/JOP.2010.000209; posted online ahead of print
at http://jop.ascopubs.org on August 4, 2011.
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SEPTEMBER 2011 • jop.ascopubs.org 323Copyright © 2011 by American Society of Clinical Oncology