**Response to PDQ Screening and Prevention Editorial Board Statements
Regarding Mammography**

**Q-1: What is the PDQ Screening and Prevention Editorial Board and what
have they recently said about the effectiveness of screening
mammography?**

**A-1:** The PDQ Screening and Prevention Editorial Board is an
independent committee of cancer experts that summarizes information from
the scientific literature about the effectiveness of cancer screening
and cancer prevention activities. The PDQ does not itself issue
guidelines or recommendations. In meetings this month, the board
discussed a paper from the Cochrane Collaboration published in *Lancet*
in October, 2001. According to reports, the Board concluded that issues
raised in the Cochrane paper should be included in a new PDQ summary on
mammography. The Cochrane paper stated that there was insufficient
evidence now available to conclude that mammography screening is
effective in reducing mortality because research studies on mammography
were flawed. The new PDQ summary, scheduled for release in April, 2002,
may include statements about the inconclusiveness of the evidence and
may state that women and their physicians should engage in a shared
decision making process to determine whether to use mammography. PDQ
statements are made available to physicians and the public on the
National Cancer Institute (NCI) Web site
([http://www.cancer.gov/cancer_information/pdq/](../(http://www.cancer.gov/cancer_information/pdq/))
and telephone information system (1-800-4-CANCER). However, these
statements are not official NCI positions and do not translate into NCI
guidelines. The current PDQ summaries state that mammography does reduce
risk of death from breast cancer. This has been the conclusion of the
PDQ Board for a number of years.

**Q-2: What is CDC's response to this news report?**

**A-2:** CDC monitors new screening research and recommendations and
uses that information in developing its cancer prevention and control
programs. At present, neither NCI nor the PDQ Board has provided new
official information for consideration. CDC reviewed the Cochrane paper
in the *Lancet* when it was published and did not find sufficient new
information to make fundamental changes in the National Breast and
Cervical Cancer Early Detection Program. Although the Cochrane Review
raises important questions about the quality of mammography research,
many other reviewers and expert panels have reviewed the same research
that the Cochrane reviewers examined and have concluded that mammography
is effective.

In the Guide to Clinical Preventive Services (2nd edition), the U.S.
Preventive Services Task Force (USPSTF) recommends routine screening for
breast cancer, with mammography alone or mammography and annual clinical
breast examination. The USPSTF is an independent, expert advisory
counsel convened by the U.S. Public Health Service. This counsel
thoroughly reviews the evidence for and against hundreds of preventive
services, including tests, immunizations, and medical interventions, and
recommends them only when there is sufficient evidence that they are
effective. The USPSTF is now completing another review of the evidence
for mammography screening.

**Q-3: What were the recent findings of the Cochrane Library review that
assessed the effectiveness of mammography?**

**A-3:** A recent article, published in the *Lancet* medical journal (v.
358, October 20, 2001), presents findings based on a review of seven
mammography studies conducted over the past several decades. The review
was conducted by the Cochrane Breast Cancer Group of the Cochrane
Collaboration[^1]. The mission of the Cochrane Collaboration, a
not-for-profit international organization, is to help people make
well-informed decisions about healthcare by preparing, maintaining, and
promoting the accessibility of systematic reviews of the effects of
healthcare interventions. The 2001 *Lancet* and Cochrane Collaboration
articles were written in response to reader responses to an earlier
article in *Lancet* (v 355, January 8, 2000) by the same authors. The
2000 and 2001 articles reached similar conclusions about the lack of
effectiveness of mammography.

Although the authors themselves did not conduct studies of mammography,
they reviewed the findings and methods from those studies. The reviewers
identified what they considered to be several problems with the
scientific methods, indicating that the studies may not have adhered to
sound scientific principles. They also found inconsistencies among the
studies in their main findings. The major problems the reviewers
identified were:

-   selection of women to participate in and/or to remain in the
    studies, which made the women in the mammography groups (those
    invited to receive mammography) different in some ways from those in
    the control groups (those not invited to receive mammography), for
    example that more women with pre-existing breast cancer were
    identified and excluded from the mammography groups than from the
    control groups

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-   differences in types of treatment provided for women with breast
    cancer in mammography groups versus those in control groups, for
    example that women in the mammography groups may have been more
    likely to receive mastectomy

-   differences between mammography and control groups in the decisions
    about whether deaths were due to breast cancer, incorrectly reducing
    the number of deaths due to breast cancer in the mammography groups

-   inconsistencies between results showing that mammography screening
    reduced deaths from breast cancer but did not reduce deaths overall

-   significant differences in findings from study to study, with two
    studies showing no reduction in deaths from breast cancer and others
    demonstrating a reduction

    According to the reviewers, the two studies they thought were
    relatively well conducted did not actually show that mammography
    reduced risk of death from breast cancer. The reviewers also argued
    that while five other studies concluded that mammography was
    effective in reducing deaths from breast cancer, these five studies
    had serious errors and could have produced incorrect evidence
    supporting the effectiveness of this screening tool.

    As a result, the reviewers stated that the conclusions previously
    maintained about the effectiveness of mammography should be
    reconsidered. Specifically, the Cochrane reviewers concluded that
    evidence does not show that women who receive mammography screening
    are less likely to die from breast cancer than women who do not have
    mammography screening, and

    the studies do not show that women who receive mammography live
    longer.

    Consequently, the researchers recommend that women, medical
    professionals, and policy makers reconsider whether or not to
    participate in, or support, mammography screening programs.

    **Q-4: What is CDC\'s response to this review of mammography\'s
    effectiveness as presented in the Lancet?**

    **A-4:** CDC takes seriously the concerns raised by the Cochrane
    reviewers as well as other published reports on breast cancer
    screening. The 2001 Cochrane review is the latest in a series of
    articles about mammography effectiveness. Concerns about the methods
    used in some of the studies and inconsistencies in results among the
    studies have been debated in a large number of published articles.
    Many of the concerns raised by the Cochrane reviewers have been
    raised previously and addressed by investigators involved in the 7
    original mammography studies. The Cochrane article lists more than
    250 articles published in this ongoing debate. Some reviewers favor
    methods and evidence from certain studies; other reviewers favor
    other studies. Most reviewers have come to the conclusion that
    mammography is effective. CDC monitors publications on the
    effectiveness of breast cancer screening and will continue to do so.

    CDC does not convene expert panels to undertake systematic reviews
    of the evidence of the effectiveness of cancer screening tests nor
    does it make cancer screening recommendations. As the Nation\'s
    Prevention Agency, CDC\'s mission in cancer is primarily two-fold:
    First, to translate the gains made in basic research into practical
    interventions for the health of our citizens. And then, to promote
    those practices on a wide-scale basis so that the public reaps the
    benefits of scientific discovery as quickly as possible.

    The CDC accepts the guidelines and recommendations of other
    well-recognized scientific groups, who have independently reviewed
    evidence from the seven original studies and concluded that
    mammography screening is effective. In the Guide to Clinical
    Preventive Services (2nd edition), the U.S. Preventive Services Task
    Force (USPSTF) recommends routine screening for breast cancer, with
    mammography alone or mammography and annual clinical breast
    examination. The USPSTF is an independent, expert advisory counsel
    convened by the U. S. Public Health Service; this counsel thoroughly
    reviews the evidence for and against hundreds of preventive services
    and them only when there is sufficient evidence that they are
    effective. Likewise, the National Cancer Institute (NCI), the
    federal government\'s premier cancer research agency, has convened
    consensus panels of scientists and practitioners to review evidence
    of the effectiveness of mammography, and those panels have concluded
    that mammography is effective. Most medical associations and other
    organizations that issue guidelines do recommend mammography for
    breast cancer screening -
    <http://www.ahcpr.gov/clinic/cpsix.htm#screening>.

    CDC has discussed the issues raised by the Cochrane review with
    other agencies and organizations and will continue to have such
    discussions as new evidence is made available. At present, the NCI
    and the USPSTF will continue to evaluate information as it is made
    available, but at this time, neither has concluded that their
    mammography screening recommendations should be changed. CDC will
    continue to follow the guidelines and recommendations set forth by
    the USPSTF and NCI for mammography. The development and changing of
    guidelines is a meticulous and deliberative process that involves
    many people, inside and outside government. Evaluating the quality
    of studies is a difficult process, and respected scientists may
    disagree.

    **Q-5: Does CDC intend to change its program activities on the basis
    of the Cochrane review?**

    **A-5:** CDC does not intend to modify its primary program
    activities related to the early detection of breast cancer on the
    basis of this new review. The National Breast and Cervical Cancer
    Early Detection Program, which funds mammography screening
    nationwide, will continue. CDC is open to changing its activities
    based on systematic review of new scientific evidence as it comes
    available, conducted by appropriate agencies and organizations.

[^1]: Olson O, Gotzche PC. Screening for breast cancer with mammography
    (Cochrane Review). In: The Cochrane Library, Issue 4, 2001. Oxford:
    Update Software.