Breast Cancer
01 November 2008

Many patients are becoming aware that we can fight breast cancer together - and I have been asked some interesting questions.

Can Mammography cause cancer!
Mammograms are performed in order to detect breast cancer early - even before the cancer is palpable.
There is a theoretical risk of developing breast cancer due to the radiation from mammography
This appears to be minute and some studies have shown it to be 8/1,000,000.
Balanced against this risk other studies show that annual screening reduces mortality by 36%
Whilst Biennial screening reduces mortality by 24%
The value of mammographic screening is less in younger women in their forties compared to older women.

Radiation risk from screening mammography of women aged 40-49 years.
Author: Feig SA; Hendrick RE
Source: J Natl Cancer Inst Monogr 1997 ;( 22):119-24
Address: Jefferson Medical College, Philadelphia, PA, USA.

Breast cancers have been demonstrated in women receiving X Ray doses of 0.25-20 Gy.  These high-level exposures to the breast occurred from the 1930s to the 1950s due to atomic bomb radiation, multiple chest fluoroscopies, and radiation therapy treatments for benign disease. Using a risk estimate provided by the Biological Effects of Ionizing Radiation (BEIR) V Report of the National Academy of Sciences and a mean breast glandular dose of 4 mGy from a two-view per breast bilateral mammogram, one can estimate that annual mammography of 100,000 women for 10 consecutive years beginning at age 40 will result in at most eight breast cancer deaths during their lifetime.

On the other hand, researchers have shown a 24% mortality reduction from biennial screening of women in this age group; this will result in a benefit-to-risk ratio of 48.5 lives saved per life lost and 121.3 years of life saved per year of life lost. An assumed mortality reduction of 36% from annual screening would result in 36.5 lives saved per life lost and 91.3 years of life saved per year of life lost. Thus, the theoretical radiation risk from screening mammography is extremely small compared with the established benefit from this life-saving procedure and should not unduly distract women under age 50 who are considering screening.

Address: MRC Biostatistics Unit, Institute of Public Health, Cambridge, United Kingdom.

Mammographic screening has a reduced effect on breast cancer mortality in women in their forties compared to older women. Explanations for this include poorer sensitivity in younger women due to denser breast tissue, as well as more rapid tumor progression, giving a shorter mean sojourn time (the average duration of the preclinical screen-detectable period). 

Markov-chain models to estimate tumor progression rates and sensitivity.  The mean sojourn time was shorter in women aged 40-49 compared to women aged 50-59 and 60-69 (2.44, 3.70, and 4.17 years, respectively).

Sensitivity was lower in the 40-49 age group compared to the two older groups (83%, 100%, and 100%, respectively). Thus, both rapid progression and poorer sensitivity are associated with the 40-49 age group.
Efficacy of screening mammography among women aged 40 to 49 years and 50 to 69 years: comparison of relative and absolute benefit.

Author: Kerlikowske K
Source: J Natl Cancer Inst Monogr 1997;(22):79-86
Address: Department of Epidemiology and Biostatistics, University of California, San Francisco, USA.

In randomized controlled trials, screening mammography has been shown to reduce mortality from breast cancer about 25% to 30% among women aged 50 to 69 years after only five to six years from the initiation of screening. Among women aged 40 to 49 years, trials have reported no reduction in breast cancer mortality after seven to nine years from the initiation of screening; after 10 to 14 years there is a 16% reduction in breast cancer mortality.

The quality and interpretation of mammographic screening trials for women ages 40-49.

Author: Glasziou P; Irwig L
Source: J Natl Cancer Inst Monogr 1997;(22):73-7
Address: Department of Social and Preventive Medicine, University of Queensland, Brisbane, Australia.

In women aged 40-49 at entry, the overall, absolute risk difference between those invited and those not was 0.0004 (95% CI: 0 to 0.0009).

Yet, what does this mean to a 40-year-old women considering screening? If 10,000 women aged 40-49 years were screened regularly, then after a decade there would be about 4 less breast cancer deaths? Is that worthwhile? This is a difficult question, and it needs to be weighed against the problems arising from false positives and ductal carcinoma in situ.

Reduced breast cancer mortality in women under age 50: updated results from the Malmo Mammographic Screening Program.
Unique Identifier: 98374940
Author: Andersson I; Janzon L
Source: J Natl Cancer Inst Monogr 1997;(22):63-7
Address: Department of Diagnostic Radiology, Malmo University Hospital, Sweden.
there was a statistically significant 36% reduction in breast cancer mortality in the intervention groups (relative risk = 0.64; 95% CI: 0.45-0.89; P = 0.009).
A harm-benefit analysis showed, however, that for every two breast cancer deaths prevented, one clinically insignificant cancer was diagnosed; for each breast cancer death prevented, 63 cancer-free women had been called back for further examinations; and for every 20 lives saved, one radiation- induced breast cancer death may have occurred. Recommendations for screening must therefore weigh mortality benefits against these negative effects.

The Gothenburg Breast Cancer Screening Trial: preliminary results on breast cancer mortality for women aged 39-49.

Author: Bjurstam N; Bjorneld L; Duffy SW; Smith TC; Cahlin E; Erikson O; Lingaas H; Mattsson J; Persson S; Rudenstam CM; Sawe-Soderberg J
Source: J Natl Cancer Inst Monogr 1997 ;(22):53-5
Address: Department of Diagnostic Radiology, Sahlgrens University Hospital, Gothenburg, Sweden.

This data suggests that mammographic screening can reduce breast cancer mortality in women under age 50, particularly if high-quality mammography is used and a short inter-screening interval is adhered to.

Periodic screening for breast cancer: the HIP Randomized Controlled Trial. Health Insurance Plan.
Unique Identifier: 98374933
Author: Shapiro S
Source: J Natl Cancer Inst Monogr 1997;(22):27-30
Address: Department of Health Policy, Johns Hopkins University, Baltimore, MD, USA.

This paper summarizes the findings of the first breast cancer screening trial, which was initiated in December 1963 to explore the efficacy of screening. Women aged 40-64 years were selected from enrollees in the Health Insurance Plan (HIP) of Greater New York and were randomly assigned to study and control groups. Study group women were invited for screening, an initial examination, and three annual reexaminations. Screening consisted of film mammography (cephalo-caudal and lateral views of each breast) and clinical examination of breasts. Breast cancer and mortality from breast cancer were examined by treatment group (study vs. control) and by entry-age subgroup. By the end of 18 years from entry, the study group had about a 25% lower breast cancer mortality among women aged 40-49 and 50-59 at time of entry than did the control group. However, to a large extent the difference among the 40-49-year-olds occurred in the subgroup with breast cancer diagnosed after these women had passed their 50th birthday, and utility of screening women in their forties is questionable.
Screening fundamentals.
Author: Smith RA
Source: J Natl Cancer Inst Monogr 1997;(22):15-9
Address: Cancer Control Department, American Cancer Society, Atlanta, GA 30329, USA.
While researchers have established the value of screening for breast cancer with mammography, with and without clinical breast examination n, age-specific analyses have led to differing opinions regarding the ages and the intervals that breast cancer screening should begin.
This article, therefore, provides a detailed, age-specific evaluation of mammography screening by assessing the severity of breast cancer, the effectiveness of earlier versus later treatment, and the accuracy and reliability of mammography.
Data from previous randomized trials and other sources are used to evaluate these criteria.
The results indicate that screening programs must have high levels of participation, achieve acceptable sensitivity (85%) and specificity (90%), adopt age-specific screening intervals, and consider how disease stage influences diagnosis.
In addition, as others have noted, the following benchmarks can be used to evaluate screening programs: (1) more than 50% of screen-detected cancers should be smaller than 15 mm;
(2) 30% or more of grade 3 cancers detected on screening should be less than 15 mm; and
(3) more than 70% of cancers detected on screening should be node negative

Author: Fletcher SW
Source: J Natl Cancer Inst Monogr 1997;(22):5-9
Address: Department of Ambulatory Care and Prevention, Harvard Medical School, Boston, MA, USA.

Randomized controlled trials of breast cancer screening have been conducted on women in their 40 s , and a reduction in breast cancer mortality has emerged after 10 to 15 years of follow-up among women offered screening in their forties. No effect appears for at least eight years, and the reason for the delay, compared to that seen in women aged 50-69, is not clear. Two possibilities include cancer-stage shift due to screening in younger women and the aging of women into their fifties during the course of screening.

Possible adverse effects of screening include radiation risk, although this is low, false-negative and false-positive screening tests, and over diagnosis due to detection of ductal carcinoma in situ (DCIS).
Author: Kopans DB
Source: J Natl Cancer Inst Monogr 1997;(22):1-3
Address: Massachusetts General Hospital, Department of Radiology, Ambulatory Care Center, Boston 02114, USA.
The data clearly show that screening women for breast cancer, on an annual basis, beginning by age 40, can reduce the death rate by approximately 24%.
It is important to separate medical and scientific analyses from the economic considerations.
Economics should not be used to influence the scientific and medical analysis of benefit.
In women aged 50 to 69. Mammography screening reduces mortality by 25% to 30%
Author: Champion VL; Menon U; McQuillen DH; Scott C
Indiana University School of Nursing, Indianapolis 46202, USA.
Source: Am J Preventive Med. 1998;14(2):111-7
The TPR ( True Positive Rate ) of mammography ranges from 83% to 95%
Whilst the FPR ( False Positive Rate) varies from 0.9% to 6.5%.

Author: Mushlin AI; Kouides RW; Shapiro DE
Source: Am J Preventive Med. 1998;14(2):143-53
Address: Department of Community and Preventive Medicine, University of Rochester Medical Center, NY 14642, USA.
Author: Rembold CM
Source: BMJ 1998;317(7154):307-12
Address: Cardiovascular Division, Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.

The number needed to screen for mammography to prevent a death from breast cancer was 2451 for 5 years for women aged 50-59

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