Synopsis
Compare surveillance, endocrine risk reduction and bilateral mastectomy using absolute benefit, medicine-specific harm, reconstructive consequences and the patient’s informed priorities.
- Risk reduction begins with a verified personal and family history, formal category and genetics input when indicated; no medicine or operation should be offered from an unverified anecdotal percentage.
- NICE offers tamoxifen for five years to premenopausal women at high risk and considers it at moderate risk, unless thromboembolic or endometrial-cancer risk makes it unsuitable.
- NICE offers anastrozole for five years to postmenopausal women at high risk and considers it at moderate risk unless severe osteoporosis is present; bone health is part of selection and monitoring.
Reasoning priorities
Quantify baseline risk over a stated horizon and establish whether moderate or high-risk prevention guidance applies.
The estimate must reflect verified history and current inputs. Medication benefit should be expressed against this absolute baseline rather than as relative reduction alone.
Worked reasoning
Illustrative worked example: a healthy premenopausal 39-year-old has a specialist-confirmed 31% lifetime breast-cancer risk, no current breast symptoms and asks about tablets rather than surgery.
- The clinic confirmed no pregnancy, no breastfeeding, no personal VTE or important thromboembolic/endometrial risk, no interacting medication and no planned operation or immobility. Her surveillance plan was current; she accepted non-hormonal contraception and had no QT-risk factors requiring screening ECGs.
- The clinician offered five years of tamoxifen under NICE high-risk guidance, explaining reduced breast-cancer incidence, the lack of demonstrated mortality benefit, adverse effects and surveillance alone. After reviewing the available decision aid, she chose medication.
- The experienced prescriber initiated tamoxifen 20 mg orally once daily within shared care, documented contraception during treatment and for 9 months after stopping, and gave written VTE, abnormal-bleeding and surgery/immobility advice.
- At her six-week review, she reported daily adherence and mild tolerable hot flushes, with no vaginal bleeding, thrombotic symptoms or new medicines. She confirmed continued non-hormonal contraception and preferred to continue treatment.
- The team recorded that observed tolerance and renewed the agreed review and surveillance plan. The example demonstrates an informed choice and early safety follow-up, not evidence that six weeks of treatment had prevented a future cancer.
Key medicines
Tamoxifen20 mg by mouth once daily for 5 years for primary breast-cancer risk reduction in an appropriately selected moderate- or high-risk adult under an experienced shared-care pathway.Exclude pregnancy before starting; use non-hormonal contraception during treatment and for 9 months after stopping, following the current Tillomed SmPC rather than older NICE timing. Tamoxifen is not recommended during breastfeeding: agree whether nursing or treatment will stop. Do not use with product hypersensitivity or concurrent anastrozole; primary prevention is also contraindicated after DVT/PE or with coumarin anticoagulants. NICE excludes candidates with a history or increased risk of thromboembolic disease or endometrial cancer. Assess other VTE risks and stop approximately 6 weeks before elective surgery; consider interruption during immobility with the prescribing team. New leg swelling, chest pain or breathlessness requires immediate assessment; stop tamoxifen if VTE develops and initiate appropriate treatment. Investigate abnormal vaginal bleeding or other new gynaecological symptoms promptly. Avoid potent CYP2D6 inhibitors where possible, including paroxetine, fluoxetine, bupropion, quinidine and cinacalcet; concurrent oral hormonal contraception or HRT is not recommended. For QT-risk factors, cardiac disease, QT-prolonging medicines or electrolyte disturbance, obtain baseline ECG and electrolytes, correct abnormalities, and repeat ECG at steady state, at least 4 weeks after starting; subsequent checks follow symptoms and changing risks. This is risk-based monitoring, not universal ECG screening. Discuss bone health in premenopausal patients. Withdraw immediately for suspected severe blistering/mucosal skin reactions and never restart after SJS/TEN; seek urgent assessment for angioedema.
Anastrozole1 mg by mouth once daily for 5 years for primary breast-cancer prevention in an appropriately selected postmenopausal adult under an experienced shared-care pathway.Contraindicated in pregnancy, breastfeeding or product hypersensitivity; do not use before menopause. If menopausal status is uncertain, confirm biochemically with LH, FSH and/or oestradiol before treatment. Avoid concurrent tamoxifen and oestrogen-containing therapy. Mild/moderate renal impairment and mild hepatic disease need no dose change; GFR below 30 mL/min or moderate/severe hepatic impairment requires individual benefit-risk assessment and cautious specialist use, not an invented reduced dose. Apply NICE CG164 prevention selection: do not offer anastrozole with a DEXA T-score at or below −2.5. The selected Milpharm SmPC separately calls T-score below −4.0 or more than two vertebral fractures unsuitable for prevention; this does not relax NICE selection. Assess baseline fracture risk and bone density where indicated, arrange repeated assessment, and start/monitor osteoporosis or osteopenia treatment when appropriate. Assess blood pressure, lipids and cardiovascular history before preventive use. Review new or worsening hypertension, lipid abnormalities or cardiovascular symptoms promptly, considering anastrozole as a contributor and reassessing whether preventive benefit still outweighs harm. Monitor arthralgia, menopausal symptoms and adherence alongside bone health.