Article by Dr Pamela Thompson Breast Physician, Fiona Stanley Hospital
An estimated 450, 000 Australian women are at moderate risk of breast cancer. Most of these women can be managed in primary care and GPs can provide guidance on preventive and surveillance options after assessing a patient’s risk.
Women at moderate risk of breast cancer
Women in the moderate category have a risk of breast cancer that is 1.5 to 3 times greater than the population average. This equates to an 18 -29 per cent lifetime risk of breast cancer, compared with 12 per cent in the general female population.
Moderately increased risk patients have:
- One 1st degree relative diagnosed with breast cancer (BC) <50yrs; or
- Two 1st or one 1st and one 2nd degree relative on the same side of the family with BC (without features of the high risk group such as bilateral BC, diagnosis <40yrs, male with BC, BC and ovarian cancer in the same woman or Jewish ancestry); or
- Two 2nd degree relatives on the same side of the family with BC, with at least one relative <50yrs.
Useful risk assessment tools include Cancer Australia’s Familial Risk Assessment – Breast and Ovarian Cancer (FRABOC) online tool and Advice about Familial Aspects of Breast Cancer and Epithelial Ovarian Cancer.
Apart from family history, several other factors can elevate a woman’s risk of breast cancer including dense breasts, previous abnormal biopsy (atypical hyperplasia or carcinoma in situ) and to a lesser degree, combined menopausal hormone therapy (MHT), increased BMI, alcohol consumption and lack of regular physical activity.
Further information about breast cancer risk factors can be found on the Cancer Australia website.
Prevention – (modifiable risk factors and chemoprevention).
Managing modifiable risk factors includes promoting breast feeding, advocating a healthy diet, regular physical activity (150 minutes moderate activity per week), avoiding post-menopausal weight gain and minimising alcohol intake.
Chemoprevention has been shown to reduce the risk of estrogen-receptor positive breast cancer. Tamoxifen, a selective estrogen receptor modulator, is now on the PBS for prevention in pre and post-menopausal women. When taken as a daily dose of 20mg for five years, primary invasive breast cancer incidence is reduced by 38 per cent with a benefit lasting for at least 20 years. However, Tamoxifen has not been shown to lower breast cancer specific or all-cause mortality. Side effects include; menopausal symptoms and a small increased risk of deep vein thrombosis, endometrial cancer and cataract.
GPs are encouraged to discuss the option of chemoprevention with patients who are at moderate risk. Further information on prescribing tips and contraindications is available on the on the Cancer Australia website and the Clinical Oncology Society of Australia website.
Risk reducing mastectomy is not recommended for women at moderately increased risk.
Surveillance – Women should remain breast aware and see their GP for annual clinical breast examination. Current EviQ guidelines recommend annual screening mammography commence at age 40, reverting to two-yearly after the age of 60. In women with a relative diagnosed <40yrs, special recommendations may apply. Mammography is not recommended for routine screening in women <35yrs. It is important to note that ultrasound has not been validated as a stand-alone screening test for breast cancer.
Women with high breast density have a greater proportion of glandular and connective tissue compared with fat. Breast density affects mammographic screening in two ways; it may mask detection of underlying cancers and it is also an independent risk factor for breast cancer. For the approximately 40 percent of women who have heterogeneously dense breasts (50 to 75 per cent density),the risk of developing breast cancer is 1.2 times greater than average. Women with extremely dense breasts (>75 per cent density) are 2.1 times more likely than average to develop breast cancer.
Increased detection of breast cancer with breast ultrasound in addition to mammography is in the order of three to four per 1000, but at a cost of a high false positive rate leading to increased recalls and a three times higher biopsy rate. Supplemental ultrasound screening in asymptomatic women with dense breasts who are at average risk is not currently recommended, however the addition of ultrasound screening for women with an intermediate risk and dense breasts is an option to increase cancer detection.1
Further Information on breast density for patients can be found on the Breast Cancer Network Australia website.
For more information please see the Breast Cancer Risk Assessment and Screening Health Pathway.
- Freer PE. Mammographic Breast Density: Impact on Breast Cancer Risk and Implications for Screening. Radiographics 2015: 35(2) 302-315