Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England

Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England
Duffy SW, Tabar L, Olsen AH, Vitak B et al
J Med Screen 2010;17:25-30

Link to Journal

Objectives: To estimate the absolute numbers of breast cancer deaths prevented and the absolute numbers of tumours over-diagnosed in mammographic screening for breast cancer at ages 50–69 years

Setting: The Swedish Two-County randomized trial of mammographic screening for breast cancer, and the UK Breast Screening Programme in England, ages 50–69 years

Methods: We estimated the absolute numbers of deaths avoided and additional cases diagnosed in the study group (active study population) of the Swedish Two-County Trial, by comparison with the control group (passive study population). We estimated the same quantities for the mortality and incidence rates in England (1974–2004 and 1974–2003, respectively). We used Poisson regression for statistical inference

Results: A substantial and significant reduction in breast cancer mortality was associated with screening in both the Two-County Trial (P < 0.001) and the screening programme in England (P < 0.001). The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 from the Two-County Trial and screening programme in England, respectively. The corresponding estimated numbers of cases overdiagnosed per 1000 women screened for 20 years were, respectively, 4.3 and 2.3 per 1000.

Conclusions: The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis. Between 2 and 2.5 lives are saved for every overdiagnosed case

The US Preventive Services Task Force recommendations on Screening Mammography flawed

Guidelines for mammography screening published by the U.S. Preventive Services Task Force (USPSTF) in November not only are based on flawed methodology, they also fail to address current breast imaging practice and data, making them obsolete, according to a critique published in this month's Journal of Diagnostic Medical Sonography

Author Kevin Evans, Ph.D., evaluated the USPSTF's report methodology and found that it did not meet established standards for systematic reviews (JDMS, January/February 2010, Vol. 26:1, pp. 19-23). Evans is chair of the radiologic sciences division in the School of Allied Medical Professions at Ohio State University in Columbus.

Evans used two resources to evaluate the USPSTF's report: the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a 27-point checklist, and the Assessment of Multiple Systematic Reviews (AMSTAR), an 11-point checklist.

The task force's report scored 7 out of 27 on the PRISMA checklist and 1 out of 11 on the AMSTAR list. These low methodological scores put in question the rigor used in developing the report, limiting it to a review of literature instead of a formal systematic review and reducing its overall scientific impact to a much lower level in the hierarchy of evidence, according to Evans.

"I picked two of the most well-known methods to evaluate systematic reviews and applied them to the report," he told AuntMinnie.com. "It's possible that USPSTF met these standards but failed to provide their methodology in the report. This becomes problematic in reading their guidelines."

The USPSTF's intention was to update its 2002 report by using other systematic reviews, meta-analyses, recently published literature, and data from the Breast Cancer Surveillance Consortium from 2000 to 2005. In its guidelines, it proposed the following, according to Evans:

• Routine screening mammography in women ages 40 to 49 years should not be conducted; rather, this process should be biennial at ages 50 to 74 years.
• A lack of published evidence currently exists to provide a guideline for screening mammography for women older than 75 years of age.
• A lack of evidence exists for assessing the benefits and harms of using clinical breast examinations for women 40 years and older.
• Self breast examination is not recommended to be taught to women by clinicians, as it is not a sensitive technique and raises a woman's level of anxiety.
• A lack of published evidence currently exists to provide a guideline about benefits and harms associated with digital mammography or MRI instead of film-screen mammography.

USPSTF used data from film-screen mammography in its report, rather than taking into consideration that digital mammography was developed to address film-screen's limitations and is in widespread use, according to Evans. In fact, one of the puzzling things about the USPSTF report is its lack of any reference to the American College of Radiology Imaging Network (ACRIN) Digital Mammographic Imaging Screening Trial (DMIST), conducted in 2005.

"USPSTF didn't make specific mention of DMIST," he said. "And yet they claim that more evidence is needed to provide a guideline about benefits and harms associated with digital mammography, instead of film-screen mammography."

"Other U.S. Preventive Services Task Force reports are routinely high quality," Evans said. "It's possible that the breast cancer screening task force did a good job but didn't spell out their methods. In any case, their report has created confusion for everyone, as well as our government officials."

If the U.S. Department of Health and Human Services had addressed the guidelines point by point, this confusion might have been put to rest earlier, Evans said.

"[After the guidelines were released], the Department of Health and Human Services responded by telling the public not to pay attention," he said. "They should have asked the USPSTF to provide an addendum with additional details on their review."

In the aftermath of the report's publication, USPSTF should take several steps to clear up the confusion, Evans wrote: It needs to provide an addendum that details its methodology, and if a systematic review as outlined by PRISMA or AMSTAR has not been conducted, it needs to be done.

"A revised set of guidelines is needed to assist patients in making the best decision about participating in screening breast examinations," he concluded.

Use of Lidocaine gel pre-mammo may help to reduce discomfort

Compression and the occasional discomfort and pain it brings in the breasts lead many women to avoid mammograms altogether.

However, results from a recent study from Boise, to be published in September 08 edition of Radiology, showed that application of lidocaine gel prior to a mammogram significantly reduced the degree of discomfort experienced.

Lambertz and colleagues recruited 418 women ages 32 to 89 who expected significant discomfort with screening mammography. Fifty-four of the women reported that they had probably or definitely delayed their mammograms due to concern over possible discomfort.

The women were randomized to receive placebos or premedication with acetaminophen, ibuprofen, and/or a local anesthetic gel followed by mammography screening. The gel was applied to the skin of the breasts and chest wall and then removed 30 to 65 minutes before mammography. The gel had no effect on subsequent image quality.

Results showed that oral medication produced no significant differences in breast discomfort, nor did other factors such as breast density. Women who received a topical application of 4% lidocaine gel, however, reported significantly less breast discomfort during mammography.

Eighty-eight percent of study participants indicated they would definitely get a mammogram the following year, and 10% said they would probably get a mammogram the following year.

"Women can now take charge of the situation," Lambertz said. "They can schedule a mammography appointment for a time in their cycle when their breasts are least tender, apply the gel at home, and travel to the appointment knowing they have taken steps toward a positive experience with this potentially life-saving procedure

Mammography screening of the elderly - controversies

Last month a paper was published in the Journal of Clinical Oncology entitled - Mammography Before Diagnosis Among Women Age 80 Years and Older With Breast Cancer from MD Anderson Cancer Center in Texas.

The study found that among those who had a mammogram every year or two before their diagnosis, 68 percent found the cancer at an early stage, compared with 33 percent of those who skipped mammograms altogether.

Their conclusion was that regular mammography among women > or = to 80 years of age was associated with earlier disease stage, although improved survival remains difficult to demonstrate. Health care providers should consider discussing the potential benefits of screening mammography with their older patients, particularly for those without significant comorbidity.

This sparked coverage by the New York Times, which did a good job of presenting the pros and cons of screening the elderly. Considering that the end point for measuring a screening program is mortality reduction, then it should be looked at in a proper light rather than just concentrating on reducing morbidity from the disease.

We have the occasional patient in San Francisco having screening mammograms in their eighties, similar to the NHS BSP in the UK, where patients can self refer. With the rising elderly population, and better breast-awareness, it may well be that we do more mammography in the elderly and reduce morbidity than we do for now.

Ultrasound screening in HIGH RISK WOMEN - article in JAMA May 2008

Wendy Berg and her ACRIN group published the results of Combined Screening With Ultrasound and Mammography vs Mammography Alone in high risk women in JAMA.

The ACRIN study in full is listed here

The JAMA abstract is here

Conclusions Adding a single screening ultrasound to mammography will yield an additional 1.1 to 7.2 cancers per 1000 high-risk women, but it will also substantially increase the number of false positives.

Accreditation for Digital Mammography

I have just posted a PDF document on the website advertising a course to see and experience a fully digital breast unit on the website - see the news at the top of the page. You could of course come and visit us at UCSF to experience this

In the USA, mammography is highly regulated under the MQSA (Mammography Standards Quality Act). Congress enacted MQSA in 1997, to ensure that all women have access to quality mammography for the detection of breast cancer in its earliest, most treatable stage.

This ensures mandatory minimum standards and accreditation of both equipment and staff

• Equipment has to be accredited each year
• Typical examinations for each breast type have to be submitted by the hospital
• Reporting mammographers have to meet a minimum number of examinations per year

As part of accreditation of mammography units (we were just commissioning a new Hologic Selenia in our screening pavillion), all 'attendings' reporting digital mammograms require 8 hours of training/background knowledge, to legally report digital mammograms. This is checked by the FDA inspectors whose job is to insure compliance with the 'Act'.

Part of the training can be with an applications specialist, enabling you to get the most from your workstation, and how to use (and not abuse) your digital workstations. We were running a breast imaging update course in San Francisco last weekend, and covered Digital Mammography with 4.5 hours of AMA accredited CME, covering all aspects of Digital, including medico-legal aspects, pitfalls in reporting, IHE applied to FFDM, review of the trials and recent reviews, the use of CAD etc.

Some of the issues of working in a mixed environment (due to economic constraints) we are encountering every day, as we work with a mix of analogue, FUJI CR and Hologic FFDM. Our workstations are Selenia's but do not display the FUJI images as intended, which is where IHE is supposed to come in and ensure that images can be displayed, independent of vendor.

Latest analysis of the DMIST trial - subset of women under 50 years

In the February edition of Radiology, Eta Pisano reports on some of the sub-group analysis of the DMIST study data.
Radiology, February 2008, Vol. 246:2, pp. 376-383
The subgroup of pre- or perimenopausal women younger than 50 years old with dense breasts was the only one for which FFDM performed significantly better than FSM.
The AUC for digital mammography was 0.79 versus 0.54 for film-screen mammography. Sixteen cancers in this group were found with digital and missed with film-screen mammography, while only two were found with film-screen and missed with digital.

The results also showed a trend toward improved accuracy of FSM over FFDM in women age 65 or over with fatty breasts, but it was not significant, according to the researchers. In this group, 15 cancers were found with film-screen mammography and missed with digital, and four were found with digital and missed with film-screen mammography