NCI's Cancer Information Systems-Bringing Medical Knowledge to Clinicians
NCI's Cancer Information Systems-Bringing Medical Knowledge to Clinicians
The information explosion in biomedical science is a fact of life.
Physicians are bombarded with medical information in textbooks,
journals, bulletins, direct mail advertising, audiotapes, videotapes,
online systems, CD-ROM, and interactive compact discs. Patients
learn about health and disease from many sources and ask their
physicians sophisticated and pointed questions. One of the major
challenges that clinicians face is how to keep up with what is
In a 1989 survey on information management, involving 520 primary
care practitioners and opinion leaders, two thirds of the physicians
surveyed felt that the volume of medical literature was unmanageable
, while 78% reported difficulty in screening out irrelevant
data when reviewing the medical literature.
Health professionals are not alone in their need for current medical
information. Patients and their families are faced with the arduous
task of interpreting information in order to make well-informed
decisions about their care. Lastly, those who bear the responsibility
of making policy decisions on health-care issues must have access
to state-of-the-art medical information.
Computerized systems for improving access to medical information
and accelerating the pace with which information in the medical
literature is translated into usable knowledge have been developed
by the International Cancer Information Center (ICIC) of the National
Cancer Institute (NCI) . These systems provide access to a
comprehensive source of bibliographic citations on published cancer
research (the CANCERLIT database) and current, peer-reviewed syntheses
of state-of-the-art clinical information on cancer (the PDQ database).
Both of these computerized information systems are designed to
assist users in maximizing their effective use of current medical
knowledge . In this paper, we will describe how these resources
are providing health professionals, patients, and policy-makers
with state-of-the-art information on cancer. The article will
focus on the PDQ database, explaining the process by which it
is updated and the variety of ways in which it can be accessed.
Physician Data Query (PDQ) is the NCI's comprehensive cancer information
database. PDQ first became available to health professionals in
1984. Since then, the scope of information it contains has expanded,
not only for health professionals but also for patients and their
families. It is comprised of three main types of information:
1. Full text statements based on the published literature that
reflect the current state-of-the-art information on the treatment,
supportive care, prevention, and screening of cancer, as well
as information about selected investigational and newly approved
2. Summaries of research protocols under evaluation in clinical
3. Directories of physicians and organizations that provide cancer
PDQ has been described as a knowledge base, as distinguished from
a database. It incorporates expert opinion in its selection of
literature and synthesizes the literature into concise, clear
summaries and recommendations. The database also contains relevant
abstracts from the CANCERLIT database. In this way, PDQ provides
a practical way of keeping up with advances from the clinical
Full Text Statements
Treatment Information--PDQ contains prognostic and treatment
information on the major types of cancer in children and adults,
including information on AIDS-related malignancies. For each major
type of cancer, there is a detailed statement on prognosis, staging,
and treatment directed to the information needs of health professionals.
Key citations to the literature are referenced, and abstracts
of these citations are available for review by the user. A limited
number of brief statements on less common cancers are also included.
In addition, PDQ provides treatment statements for patients and
their families that contain similar information written in nontechnical
In August, 1994, the International Cancer Information Center (ICIC)
made awards to patient educators at eight cancer centers who submitted
proposals to perform demonstration projects designed to evaluate
PDQ's patient information statements. The objectives of the project
are to encourage the development of interventions in clinical
settings that will increase the use of the PDQ patient information
statements; encourage centers to use these statements as an established
resource; increase knowledge and understanding of NCI educational
and scientific resources; ensure that cancer patients are receiving
information on state-of-the-art cancer treatment options to help
them make informed decisions regarding their care; increase the
efficiency and efficacy of cancer patient education efforts; and
define the role of PDQ as one of several patient education resources.
Supportive Care Information--PDQ contains supportive care
statements describing the pathophysiology and treatment of common
complications of cancer and its treatment, such as pain, hypercalcemia,
and nausea/vomiting. Each statement generally contains an overview,
information on etiology, assessment and management, and references
to the current literature.
Screening and Prevention Information--The screening information
in PDQ includes statements on screening for nine cancers: breast,
cervical, oral, skin, colorectal, prostate, testicular, ovarian,
and gastric. Each statement contains a summary of the available
data concerning screening for that particular disease site, the
levels of evidence for that summary (Table 1), and the significance
and evidence of benefit for the summary statement. The statements
also include references to the current literature that support
the information in the statement.
In early 1994, information on cancer prevention was added to PDQ.
The first statements are on prevention of aerodigestive cancers,
cervical cancer, colorectal cancer, and skin cancer. Similar in
format to the PDQ information on screening, these statements will
also contain a summary of data concerning prevention for that
particular disease site, levels of evidence for that summary (Table
2), and the significance and evidence of benefit for the summary
Investigational and Newly Approved Drug Information--Currently,
there are 11 statements on investiga- tional and newly approved
anticancer agents. The statements include a description of each
drug, its mechanism of action, indications and contraindications,
interactions, dose schedules and modifications, and pharmaceutical
The Review Process--Information in the PDQ statements is
peer-reviewed by five core editorial boards, one for each type
of information covered by the cancer information statements: Adult
Treatment Editorial Board, Pediatric Treatment Editorial Board,
Supportive Care Editorial Board, Screening and Prevention Editorial
Board, and Drugs Under Clinical Investigation Editorial Board.
Board members have the task of translating information culled
from the medical literature into medical knowledge that can be
effectively used by health professionals.
The core boards are comprised of 65 cancer specialists, the majority
of whom are not government employees. Each core editorial board
is supplemented by an external advisory board that reviews the
statements at least once a year. The external advisory boards
are comprised of over 100 physicians and other health professionals
with special expertise in the diagnosis, prevention, treatment,
and supportive care of cancer. Members of the core and external
advisory boards oversee the development and maintenance of the
cancer information in PDQ. The core boards meet regularly to discuss
recent literature and to develop new state-of-the-art statements
or revise existing statements. The boards base their recommendations
on the scientific literature and the clinical expertise of its
core and external advisory members.
To assist board members in reviewing the medical literature effectively
and promptly, a process has been developed to provide them with
appropriate information (see Figure). Each month, professionals
review the tables of contents of more than 70 biomedical journals
to identify articles of potential relevance. After reviewing these
articles, NCI staff forward the articles of highest potential
relevance and scientific validity to appropriate editorial board
members. In some cases, the boards also review prepublication
data. For example, treatment statements on breast and prostate
cancer were revised based on recommendations made at the NIH Consensus
Development Conferences while the reports were still in draft
The board members suggest and the editor-in-chief chooses topics
to be discussed at the next board meeting, including important
changes to the state-of-the-art statements, such as the deletion
or addition of a treatment to the list of standard treatment options.
When there is disagreement about the interpretation of data, PDQ
statements address the controversial nature of the topic.
The methods used for developing and maintaining the content of
the PDQ cancer information statements vary from one editorial
board to another. For example, the Adult Treatment Board members
maintain the treatment statements through informal consensus development.
Before each board meeting, members are asked to evaluate specific
articles regarding their appropriateness for inclusion in existing
cancer treatment statements. At the meeting, members discuss the
positive and negative aspects of each article or report, and make
decisions as to whether the statements should be modified based
on this information. Treatment options deemed appropriate are
included but are not usually accorded any particular weight. Pertinent
articles are listed for each option so that users can make their
own treatment decisions based on the current literature.
Board members, concerned with the growing volume of medical knowledge
and the increased emphasis on physician accountability and cost-effective
practice, are considering ways to assist physicians in understanding
the available medical literature and in applying it when making
treatment decisions. Toward this end, the Adult Treatment Board
members are moving toward an evidence-based approach for evaluating
new information, a method already used by members of the Screening
and Prevention Board. This approach has proven to be well suited
to the controversial nature of much of the scientific data on
cancer screening and prevention. It allows the Screening and Prevention
Board members to summarize the information currently available
on a particular topic, and to indicate the strength of the available
evidence. Although the summaries are very concisely written, they
afford the user a good understanding of the particular method
of cancer screening or prevention and the strength of the data
The practice of developing evidence-based summaries of the existing
literature often draws attention to significant gaps in medical
evidence. Pointing out these gaps is not only important for physicians
and patients making personal decisions about screening and prevention,
but also helps to define areas that are most in need of additional
research. Each screening or prevention statement also includes
text discussing the background information from which the summaries
were derived. The formal levels of evidence used by the Screening
and Prevention Board to evaluate the strength of available information
are shown in Tables 1 and 2.
The use of an electronic medium to disseminate current information
enables the boards to revise the statements constantly as new
information becomes available. PDQ's cancer information statements
are quite dynamic. On average, 30 of the 210 statements were revised
each month over the past year. While many of these changes represent
the addition of new literature references, about 90% of the changes
were revisions of the statements themselves. About 30% of the
statements changed each month have undergone substantial revisions.
It is a mandatory requirement to all PDQ vendors that all data
carry the date of retrieval. This indicates to the user whether
the version they have is current.
PDQ contains more than 1,500 summaries of clinical trials that
are open or approved for patient accrual, including protocols
for cancer treatment, supportive care, and screening and prevention.
For each trial, detailed summaries are prepared from the original
protocol document, ensuring uniformity and accuracy of the content.
PDQ protocols can be retrieved by diagnosis, treatment modality,
phase, locality, and drug name, or any combination of these
All protocols supported by the NCI are listed in PDQ. Board members
review protocols submitted by investigators who are not directly
supported by the NCI prior to their inclusion in PDQ. The criteria
for evaluating voluntary research protocol submissions are shown
in Table 3. Foreign protocols and clinical trials that are not
supported by the NCI are included after review and approval using
a process sanctioned by the PDQ Editorial Board. In addition,
there are more than 7,000 summaries of protocols that have been
completed or are no longer accepting patients.
PDQ provides a source of information on previous and ongoing clinical
cancer research whether the results are positive or negative.
For physicians, the ability to easily retrieve these data is essential
to responsibly planning the use of cancer treatment resources.