Primary prevention

Primary prevention of breast cancer in situ focuses on reducing invasive breast cancer risk.[51]

Options include risk-reducing agents (hormone therapies) and surgery (mastectomy). These options should be discussed with women at risk for breast cancer, and decisions should be based on shared decision-making.[52]

Women should be advised on healthy lifestyle measures that may reduce their risk, such as limiting alcohol consumption, keeping physically active, maintaining a healthy weight, and, if appropriate, breastfeeding.[52]

Risk-reducing salpingo-oophorectomy may be considered for women with certain pathogenic germline variants (e.g., BRCA1, BRCA2) that confer elevated risk for ovarian and breast cancer. See Primary invasive breast cancer.

Breast cancer risk assessment

Risk assessment should be used to identify women at higher risk, and to guide screening, risk reduction strategies, and genetic evaluation.[52][53]

Breast cancer risk reduction measures may be considered following evaluation using a validated risk assessment tool, such as the National Cancer Institute’s Breast Cancer Risk Assessment Tool (BCRAT; also known as the Gail model) which determines risk based on:[54] National Cancer Institute: breast cancer risk assessment tool Opens in new window

  • Current age

  • Age at first menstrual period

  • Age at first live birth

  • Number of first-degree relatives with breast cancer

  • Number of breast biopsies

  • Presence atypical hyperplasia

The BCRAT (Gail model) applies to women aged 35-85 years. It is not accurate in the setting of prior ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), or invasive breast cancer. Risk may be underestimated in: those with BRCA1 or BRCA2 mutation; those with a strong family history of breast cancer; those with a family history of ovarian cancer in the maternal or paternal family lineage; non-white individuals; and those with atypical hyperplasia.[52]

Other validated assessment risk tools that can be used to estimate breast cancer risk, include:[52]

US guidelines recommend clinical assessment by age 25 years for all women.​[53][55][56][57]​​ Clinical assessment should include risk assessment, counselling on breast awareness and healthy lifestyle, and may include a breast examination.

Risk-reduction options should be discussed with women at increased risk of breast cancer who have a life expectancy ≥10 years, including those who have:[52]

  • Known germline pathogenic/likely pathogenic variants conferring elevated risk for breast cancer

  • Prior thoracic radiotherapy between age 10 and 30 years (e.g., to treat Hodgkin's lymphoma)

  • Personal history of atypical hyperplasia/LCIS

  • Strong family history of breast cancer

  • Elevated risk of breast cancer based on a validated risk-estimation model

Risk-reducing agents

Chemoprevention with risk-reducing agents (e.g., tamoxifen, raloxifene, anastrozole, or exemestane) is recommended for women aged ≥35 years at high risk of developing breast cancer (e.g., 5-year breast cancer risk of ≥1.7% using the Gail model; or a 10-year risk of ≥5% using the IBIS/Tyrer-Cuzick model; or with a history of atypical hyperplasia or LCIS).​[52]​​[58][59][60]

Tamoxifen is indicated for chemoprevention in pre- and postmenopausal women. Tamoxifen is a teratogen and should be avoided in pregnancy or in women planning a pregnancy.[52] 

Raloxifene and aromatase inhibitors (e.g., anastrozole or exemestane) are recommended for chemoprevention in postmenopausal women only.[52]​​[58][59][60]​​​​

Risks and benefits of risk-reduction agents should be discussed, including adverse effects and age-dependent risks, and a shared decision made. According to the National Comprehensive Cancer Network (NCCN) breast cancer risk reduction expert panel, tamoxifen is a superior choice of risk reduction agent for most postmenopausal women.[52] However, consideration of adverse effects may lead some women to choose raloxifene in preference to tamoxifen.[61][62]

The US Preventive Services Task Force (USPSTF) specifically recommends against the routine use of risk-reducing agents for women who are not at increased risk for breast cancer.[60]

Investigations before starting a risk-reducing agent

Women with an intact uterus require a gynaecological evaluation before starting tamoxifen, to ensure there is no abnormal vaginal bleeding that requires further investigation.[52]

Postmenopausal women require an assessment of bone density (with dual energy x-ray absorptiometry [DEXA] scan) before treatment and should be offered raloxifene or tamoxifen in preference to aromatase inhibitors if they have low bone mineral density.[52]

Women who do not desire risk-reducing therapy should be invited for screening according to national guidelines.

Risk-reducing mastectomy

Prophylactic mastectomy should be discussed and can be considered for breast cancer risk reduction in women with:[52][63][64]​​

  • Germline pathogenic/likely pathogenic variants in high penetrance breast cancer susceptibility genes (e.g., BRCA1, BRCA2)

  • Compelling family history

  • History of chest wall radiation before 30 years of age

Prophylactic mastectomy in BRCA carriers is associated with reduced breast cancer incidence and reduced breast cancer mortality.[65]​ Risk-reducing mastectomy is most beneficial when carried out in women aged between 30 and 55 years.[36]

Women considering surgery should undergo multidisciplinary evaluation and receive counselling on the potential psychosocial impact of risk-reducing mastectomy. Immediate breast reconstruction is an option for many women undergoing risk-reducing mastectomy.[52] Nipple-sparing mastectomy may be an alternative option to total mastectomy.[36]

For women who decline risk-reducing mastectomy, risk-reducing agents may be considered for women with BRCA1 or BRCA2 variants.[36] However, evidence for risk-reducing agents is lacking for all pathogenic variants and for women with prior thoracic radiotherapy.[52] Recommendations for screening according to risk should be followed. See Screening.​​

Contralateral prophylactic mastectomy is not recommended for patients diagnosed with unilateral breast cancer, unless they already meet criteria for risk-reducing mastectomy based on high familial or genetic risk.[66]​ One meta-analysis found that there was no absolute reduction in the risk of metachronous contralateral breast cancer in patients who received a contralateral prophylactic mastectomy, compared with those who did not have the procedure.[67] In patients with elevated familial or genetic risk, contralateral prophylactic mastectomy significantly decreased the risk of metachronous contralateral breast cancer, compared with no procedure, but there was no improvement in breast cancer mortality or overall survival. 

Lifestyle measures

Healthy lifestyle including physical activity and a balanced diet may prevent breast cancer.[68] In the Women's Health Initiative randomised controlled study, those who consumed a low-fat diet had a reduced risk of death after a diagnosis of breast cancer compared with those who consumed a usual diet.[69] The positive association between alcohol consumption and breast cancer risk is well established.[70] A study among patients attending breast clinics or screening found low levels of alcohol health literacy in this group. These appointments could provide an opportunity for discussing alcohol use as a modifiable risk factor.[71]

Secondary prevention

Avoiding hormone replacement therapy (HRT) could reduce breast cancer recurrence, or the progression of ductal carcinoma in situ (DCIS) to invasive breast cancer.[17][166]​​​​ Systemic HRT is not routinely recommended for women with menopausal symptoms who have a history of breast cancer.[95][167]

If DCIS develops during HRT, alternatives should be sought to treat menopausal symptoms.

Chemopreventive agents

Tamoxifen is a selective oestrogen receptor modulator (SERM) that can be used to prevent recurrence or new breast cancer in pre- and postmenopausal women.[150] [ Cochrane Clinical Answers logo ] ​ Tamoxifen can be taken for up to 5 years. Tamoxifen is indicated for chemoprevention in pre- and postmenopausal women. 

Raloxifene is approved by the US Food and Drug Administration (FDA) for the prevention of invasive breast cancer in high-risk postmenopausal women and in women at risk for osteoporosis. Prolonged use of raloxifene (>4 years) does not appear to be harmful in the context of osteoporosis.[168] Aromatase inhibitors have been shown to decrease risk of recurrence after treatment for DCIS in postmenopausal women.[169][170]

Tamoxifen, raloxifene, exemestane, or anastrozole are recommended options for chemoprevention in postmenopausal women.[52] According to the National Comprehensive Cancer Network (NCCN) breast cancer risk reduction expert panel, tamoxifen is a superior choice of risk reduction agent for most postmenopausal women.[52] However, consideration of adverse effects may lead some women to choose raloxifene in preference to tamoxifen.[61][62]

Women with lobular carcinoma in situ (LCIS)

These patients are considered high-risk (based on the Gail model) and should be offered chemoprevention to reduce the risk of invasive cancer, discussing the benefits and risks of the intervention. Chemoprevention with risk-reducing agents is recommended for women age ≥35 years who have a history of LCIS.[52][58][59][60]

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