1. Over-diagnosis from mammography screening

NBOCC position statement.
Created: January 2008
Updated: 2014

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 per cent to 13 per cent 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. 

2. BreastScreen WA Thyroid Guard Statement

Having a mammogram with BreastScreen WA DOES NOT require a “thyroid guard”.

From time to time, information circulates via emails and social media about "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.

References:

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.

BreastScreenWA: 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. The harm/benefit ratios for mammography screening in women with Down syndrome are not as favourable as those for average-risk women. 

Women with Down syndrome have a very low risk of breast cancer and a greater risk of complications from surgical procedures. People with Down syndrome are also known to have an increased risk of certain cancers, other than breast cancer, due to their DNA being more sensitive to the radiation used in X-rays.

A woman should discuss alternatives to mammographic screening with her doctor; this may include regular clinical breast assessments. 

References:

1. Alagoz O, Hajjar A, Chootipongchaivat S, van Ravesteyn NT, Yeh JM, Ergun MA, de Koning HJ, Chicoine B, Martin B. Benefits and Harms of Mammography Screening for Women With Down Syndrome: a Collaborative Modeling Study. J Gen Intern Med. (2019), 34(11): 2374-2381. doi: 10.1007/s11606-019-05182-5. Epub 2019 Aug 5. PMID: 31385214; PMCID: PMC6848489.  

2. 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.  

3. Hasle H, Clemmensen IH, Mikkelsen M. Risks of leukaemia and solid tumours in individuals with Down’s syndrome. Lancet (2000), 355: 165-159.  

4. 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.  

5. 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.  

6. 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. Position Statement on the use of Tomosynthesis with BreastScreen Australia Services

Digital Breast Tomosynthesis (3D Mammography) uses a modified Digital Mammogram Machine, with conventional X-rays taken at multiple projections and a digital detector with mathematical computations to create cross sectional images of the breast tissue. The slices reduce the issue of overlapping tissue and enhance the visualisation of lesion margins. From 1st November 2018, a Medicare Benefits Schedule (MBS) Item will be available to women referred for diagnostic breast imaging. This is time-limited MBS funding. The new items are an interim measure (for two years) to enable an application for long-term funding to be lodged by the diagnostic imaging sector. Tomosynthesis can be utilised for diagnostic imaging in women with breast symptoms or for surveillance of women with a family history or past history of breast cancer.

There is no current evidence that Tomosynthesis is appropriate for Population Breast Cancer Screening through BreastScreen WA.

There is currently no evidence that Tomosynthesis;

1. Leads to a reduction in Breast Cancer Mortality superior to conventional Screening Mammography
2. Leads to a reduction in interval cancers (cancers that present as symptomatic cancers within 2 years of a normal screening examination)
3. Reduces the incidence of overdiagnosis of breast cancer (the detection of cancers that would not have been become clinically significant in a women’s lifetime)

BreastScreen Australia, is actively reviewing the published medical evidence on Tomosynthesis, and future decisions on breast cancer screening technology will be based on the best robust medical evidence as that evidence emerges. At this time, two-view mammography continues to be the most effective population primary screening test for breast cancer. More information.

5. Position Statement on Thermography

BreastScreen Australia, Cancer Australia and The Royal Australian and New Zealand College of Radiologists do not recommend the use of thermography for the early detection of breast cancer. Screening mammography is the only evidence based imaging modality shown to reduce breast cancer mortality. There is no current scientific evidence to support the use of thermography in the early detection of breast cancer and in the reduction of mortality.

For further information please refer to:

• Cancer WA's unproven breast imaging fact sheet
• Cancer Australia's Thermography position statement

FAQs about BreastScreen WA

You may also find other information about BreastScreen WA in the FAQ section.