1. Over-diagnosis from mammography screening
NBOCC position statement.
Created: January 2008
Updated: September 2010
Developed by National Breast and Ovarian Cancer Centre (NBOCC).
Endorsed by the Cancer Institute NSW and The Cancer Council Australia.
Mammography screening significantly reduces death rates from breast cancer by enabling earlier and more effective treatment.
Most breast cancers found through screening are progressive and would become symptomatic within the women's lifetime if left untreated. It is likely, however, that there is a sub-set that would be non-progressive or progress so slowly that they would not otherwise be found in a woman's lifetime.
Estimates of the size of this sub-set vary widely and are dependent on study design and research assumptions. While a range of 5% to 13% of all breast carcinomas was cited in the first position statement of the National Breast and Ovarian Cancer Centre as a plausible estimate of levels of over-diagnosis, publications since then have provided such widely varying estimates that a summary pooled estimate cannot be derived with any confidence.
Research is underway, including molecular and genetic research, to find means of identifying cancers at minimal risk of progression.
For complete articles with references, please go to Cancer Australia.
2. BreastScreen WA Thyroid Guard Statement
Having a mammogram with BreastScreen WA DOES NOT require a “thyroid guard”
Recently there has been an e-mail going around about the increased risk of thyroid cancer related to mammography and women are encouraged to request a "thyroid guard" to wear when having a mammogram.
BreastScreen WA do not have, or need, "thyroid guards" as radiation risk to the thyroid from a mammogram is negligible, (not worth considering), because the x-ray beam is narrowly focussed to only target the breast area.
The risk of getting thyroid cancer from a screening mammogram is considered to be extremely low. A screening mammogram uses minimal doses of radiation (about 0.7mSv for 4 X-rays).
The BreastScreen WA mammography machines are routinely serviced and compliance tested to meet WA Radiological Council requirements.
More information on radiation
1. Whelan C, McLean D, Poulos A. Investigation of thyroid dose due to mammography. Australasian Radiology (1999), 43: 307 -310.
2. Schonfeld SJ, Lee C, Berrington de Gonzalez A. Medical Exposure to Radiation and Thyroid Cancer. Clinical Oncology (2011) 1-7.
BreastScreen WA: Thyroid Guard Statement, April 2011
3. Screening mammography for women who have Down syndrome
Mammographic screening may not be beneficial for women with Down syndrome. Women with Down syndrome have a very low risk of breast cancer and are sensitive to the radiation used in X-rays, including mammography X-rays. A woman should discuss alternatives to mammographic screening with her doctor; this may include regular clinical breast assessments.
1. Chicoine B, Roth M, Chicoine L, Sulo S. Breast cancer screening for women with Down syndrome: lessons learned. Intellect Dev Disabil (2015), 53(2):91-99.
2. Hasle H, Clemmensen IH, Mikkelsen M. Risks of leukaemia and solid tumours in individuals with Down’s syndrome. Lancet (2000), 355: 165-159.
3. Satg’e D, Sasco AJ, Pujol H, Re’thore’ M-O. Les cancers mammaries des femmes trisomiques 21. Bulletin de l’Academie Nationale de Medecine (2001), 185: 1979-1980.
4. Sanford KK, Parshad R, Price FM, Tarone RE, Schapiro MB. X-ray induced chromatid damage in cells from Down syndrome and Alzheimer disease patients in relation to DNA repair and cancer proneness. Cancer Genetics and Cytogenetics (1993), 70: 25-30.
5. Scholl T, Stein Z, Hansen H. Leukemia and other cancers, anomalies and infections as causes of death in Down’s syndrome in the United States during 1976. Developmental Medicine and Child Neurology (1982), 24: 817-829.
4. BreastScreen WA Dense Breast Statement
Position Statement about Breast Density for GPs
On a mammogram, fatty tissue appears black and normal breast tissue and fibrous supportive tissue appears white or ‘dense’. Thus breast density has the potential to obscure significant breast lesions such as cancers that also appear as white shapes in the image.
BreastScreen WA recognises that breast density has an important impact on mammographic screening. Increased breast density is associated with an increased risk of breast cancer while leading to a lower accuracy or ‘sensitivity’ for cancer detection.
BreastScreen WA acknowledges that this is a complex issue and supports the following excerpts from the American College of Radiology (ACR) statement of 24 April 2012.
- The assessment of breast density is not reliably reproducible. When the same mammogram is interpreted by a different physician or by the same physician on different occasions, differing density can be reported. If these variations are reported to each woman screened on each occasion, it might result in confusion or an impression of the lack of reliability of mammography.
- For women with fatty breasts, the reporting of this information may convey a false sense of security about negative mammography results. Even women with fatty breasts may have breast cancer undetected by mammography and may present with a palpable finding. High-risk women should not be complacent and forego recommended Screening MRI because they have fatty breasts.
- The significance of breast density as a risk factor for breast cancer is highly controversial. Moreover, there is no consensus that density per se confers sufficient risk to warrant supplemental screening. For women with dense breasts, receipt of breast density information may create undue anxiety about their risk and worry that mammography may have missed a breast cancer.
- The inclusion of breast density information in the lay summary could result in demands for additional non-mammographic screening. Both ultrasound and magnetic resonance imaging (MRI) have been studied as supplemental screening techniques, primarily in higher risk women, and both can detect malignancies undetected via mammography. Breast MRI is more sensitive than either mammography or ultrasound and can detect malignancies not found when both screening mammography and screening ultrasound are combined. Importantly, both additional techniques result in additional false positive examinations and increase the number of benign breast biopsies. Also, it needs to be remembered that there is no randomized trial data that shows that adding either ultrasound or MRI to mammography screening saves lives.
- Unless supplemental screening were reimbursed by insurers, there may be an unfortunate disparity between women who can afford to pay for the additional screening exam and those who cannot.
Women with dense breasts have a moderately increased risk of breast cancer and mammography is less sensitive. Interval cancers that arise following a normal mammogram result and before the next mammogram is due are more prevalent in this group of women. It is particularly important for women with dense breasts to be breast aware, and seek medical attention for any new breast symptom.
Until such time that more coherent research evidence is available on how women with very dense breasts should be managed, BreastScreen WA is recommending to women with dense breasts that they see their GPs for regular breast examinations and that women with signs or symptoms of possibly significant breast disease be referred for additional breast imaging.
American College of Radiologists. (2012) ACR Statement on Reporting Breast Density in Mammography Reports and Patient Summaries, April 24, 2012.
5. Position Statement on the use of Tomosynthesis with BreastScreen Australia Services
The Standing Committee on Screening recommends that, based on current evidence, the use of tomosynthesis as a screening technology in BreastScreen Australia be confined to clinical trial settings. Two-view mammography remains the most effective screening test at this time. Tomosynthesis can be of benefit in an assessment setting. More information