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NCI's Cancer Information Systems-Bringing Medical Knowledge to Clinicians

NCI's Cancer Information Systems-Bringing Medical Knowledge to Clinicians

The National Cancer Institute's computerized information systems have been designed to help physicians cope with the information explosion by translating the medical literature into usable forms. Systems developed by the NCI's International Cancer Information Center provide access to a comprehensive source of bibliographic citations on cancer research (the CANCERLIT database) and to current, peer-reviewed syntheses of state-of-the-art clinical information on cancer (the PDQ database). This article describes how the PDQ databases were developed and are kept up-to-date, and how physicians and other health professionals can access PDQ and other NCI information by computer and fax.


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 important.

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 [1], 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) [2]. 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 [3]. 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)

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 anticancer drugs.

2. Summaries of research protocols under evaluation in clinical trials.

3. Directories of physicians and organizations that provide cancer care.

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 literature.

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 language.

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 statement.

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 information.

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 stage.

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 supporting it.

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.

Research Protocols

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.


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