Hormonal anticancer therapy

01Purpose and principlesWhat the treatment does and how it fits into care.

Hormonal cancers depend on steroid-hormone signalling to varying degrees. In oestrogen-receptor-positive breast cancer, endocrine therapy reduces recurrence or controls advanced disease. Ovarian function determines whether aromatase inhibition alone can suppress oestrogen adequately. In prostate cancer, medical or surgical castration lowers testosterone, while receptor-pathway inhibitors deepen blockade. Histology, receptor status and disease setting define the evidence-based sequence.

Because endocrine therapy is prolonged, low-grade toxicity can erode adherence. Vasomotor symptoms, arthralgia, fatigue, vaginal or sexual symptoms, mood change and altered body composition should be asked about directly. Drug interactions matter: enzyme inhibition can affect tamoxifen activation, and agents can influence anticoagulation or cardiovascular medicines. Pregnancy prevention and fertility discussion precede treatment where relevant.

Monitoring combines cancer outcome with long-term health. Bone density and fracture risk, blood pressure, glucose, lipids and cardiovascular symptoms are assessed according to agent and duration. Unexpected bleeding on tamoxifen requires gynaecological assessment; aromatase-inhibitor musculoskeletal symptoms need diagnostic review before being assumed; androgen deprivation requires exercise, metabolic and bone protection.

Key points

Endocrine therapy deprives a hormone-dependent tumour of ligand or blocks its receptor; it is central to many breast and prostate cancer pathways.
Treatment is selected by receptor or disease biology, menopausal or gonadal status, stage, prior exposure, comorbidity and treatment intent.
Breast strategies include oestrogen-receptor modulation, aromatase inhibition, oestrogen-receptor degradation and ovarian suppression in defined combinations.
Prostate strategies reduce androgen production or receptor signalling; some agents cause an initial testosterone surge and need pathway-specific flare protection.
Endocrine treatment is often taken for months or years, making adherence, interactions and cumulative quality-of-life effects decisive.
Bone loss, vasomotor symptoms, sexual dysfunction, infertility, metabolic change and cardiovascular risk require proactive discussion and prevention.
Tamoxifen-associated thrombosis and endometrial symptoms, aromatase-inhibitor bone loss, and androgen-deprivation metabolic and skeletal harms differ and must not be conflated.
New bleeding, chest pain, unilateral swelling, neurological deficit or severe mood change requires prompt assessment rather than routine side-effect reassurance.

02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.

Hormone-receptor-positive disease

Validated tumour receptor or disease context predicts that reducing hormone signalling can alter recurrence or progression.

Ovarian function relevant

Premenopausal ovarian activity can make aromatase inhibition alone ineffective, requiring status confirmation and pathway-defined suppression.

Thrombotic warningRed flag

New unilateral swelling, chest pain, breathlessness or neurological deficit during selective oestrogen-receptor modulation needs urgent thrombosis assessment.

Skeletal toxicity

New fragility fracture, height loss or progressive bone pain during long-term hormone deprivation requires fracture and metastasis evaluation.

Metabolic and sexual burden

Weight change, diabetes risk, erectile or vaginal symptoms and low mood may reflect treatment and materially affect adherence.

03Assessment before treatmentTests and checks that guide safe selection.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Tumour receptor and pathology reviewFirst step
Why
Confirm that endocrine treatment matches the cancer biology.
Interpretation and limitations
Use validated receptor reporting and current disease setting; low or heterogeneous expression requires tumour-specific MDT interpretation.
02
Menopausal or gonadal assessment
Why
Select an effective suppression or blockade strategy.
Interpretation and limitations
Clinical history, treatment-induced amenorrhoea and selected hormones are interpreted cautiously because chemotherapy and suppression alter assays.
03
Bone health assessment
Why
Establish fracture risk before prolonged hormone deprivation.
Interpretation and limitations
Use history, calcium and vitamin D context and bone-density or risk tools according to pathway; metastatic bone pain needs separate imaging.
04
Cardiometabolic baseline
Why
Identify blood-pressure, lipid, glucose and vascular risks likely to worsen.
Interpretation and limitations
Optimise modifiable disease without delaying necessary cancer treatment and repeat measurements at agent-specific intervals.
05
Response assessment
Why
Determine whether treatment controls cancer in the relevant setting.
Interpretation and limitations
Use symptoms, examination, imaging and tumour-specific markers together; marker change alone should not overrule clinical progression.

04Treatment approachPreparation, options, escalation and aftercare.

01SelectMatch biology and endocrine stateFirst stepHormone-sensitive breast, prostate or another cancer is confirmed.

1Define stage, intent, receptor biology, menopausal or gonadal status, prior treatment and important vascular or skeletal comorbidity.
2First lineChoose the current tumour-specific first-line endocrine option or combination and explain expected duration, onset and alternatives.
3Address fertility, contraception, sexual health, bone and cardiometabolic risk before treatment begins.

02SupportMaintain effective long-term treatmentThe patient is taking endocrine anticancer medicine over repeated months or years.

1Ask directly about adherence, hot flushes, pain, fatigue, mood, sexual symptoms and practical medicine barriers at each review.
2Manage agent-specific toxicity, interactions, exercise, bone protection and cardiometabolic risks rather than accepting silent discontinuation.
3Investigate red flags such as postmenopausal bleeding, thrombosis symptoms or focal bone pain through the appropriate urgent pathway.

03ChangeRespond to progression or intoleranceDisease progresses or toxicity threatens continued treatment.

1Confirm adherence, interaction, endocrine state and objective progression before declaring biological resistance.
2Switch, combine or discontinue according to disease-specific sequencing and mutation or receptor evidence where validated.
3Revisit goals, competing systemic options and symptom care, documenting whether the change is for resistance, harm or preference.

05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.

Selective oestrogen-receptor modulation for appropriate early and advanced hormone-receptor-positive breast cancer, including many patients with functioning ovaries.

Tamoxifen

20 mg orally once daily for hormone-receptor-positive breast cancer; duration and any extension are set by the disease stage, menopausal status, recurrence risk and current breast protocol.

Counsel about venous thromboembolism, vasomotor symptoms and endometrial pathology; investigate abnormal vaginal bleeding and review pregnancy risk, ocular symptoms and strong CYP2D6 inhibitors.

Aromatase inhibition for eligible hormone-receptor-positive early or advanced breast cancer.

Letrozole

2.5 mg orally once daily in an indicated postmenopausal breast-cancer setting, or only with confirmed ongoing ovarian suppression when used before natural menopause; follow the tumour protocol for duration and sequencing.

Do not use an aromatase inhibitor alone when ovarian function persists. Assess bone density and fracture risk, lipids, arthralgia, adherence and signs of ovarian escape during pharmacological suppression.

GnRH agonist that suppresses gonadal steroid production in hormone-sensitive prostate cancer and selected premenopausal breast-cancer pathways.

Leuprorelin 3-month depot

11.25 mg as a single subcutaneous depot injection every 3 months for prostate cancer or an authorised breast-cancer ovarian-suppression indication; when combining with an aromatase inhibitor, establish and confirm ovarian suppression as the product information directs.

Initial testosterone flare can worsen obstruction, bone pain or cord risk and may require protocol-defined flare protection. Monitor metabolic, cardiovascular, skeletal, sexual and mood effects, injection timing and adequacy of suppression.

06Complications, monitoring and follow-upAdverse effects, response and longer-term review.

Track dispensing and patient-reported adherence because missed long-term tablets can look like biological treatment failure.
Review thrombotic, gynaecological, musculoskeletal, vasomotor, sexual and mood symptoms according to the actual medicine.
Monitor bone density or fracture risk and ensure calcium, vitamin D, exercise and antiresorptive decisions follow the cancer pathway.
Measure weight, blood pressure, glucose and lipids during prolonged androgen deprivation or relevant endocrine regimens.
Assess cancer response with site-specific examination, imaging and markers at the planned interval, escalating clinical progression even if one marker is stable.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Amenorrhoea is not menopause

Chemotherapy can stop bleeding temporarily while ovarian oestrogen production later recovers, affecting aromatase-inhibitor effectiveness.

Adherence is biological

A highly effective medicine cannot reduce recurrence when symptoms, cost or misunderstanding lead to unreported non-use.

Bone pain has two paths

Treatment-related arthralgia is common, but focal progressive pain still requires assessment for fracture or metastasis.

Flare is predictable

Some androgen agonists initially increase testosterone, so obstruction or painful metastases need the protocol's preventive strategy.

Risk is medicine-specific

Thrombosis, endometrial, skeletal and metabolic harms vary; counselling should not merge all endocrine therapies into one side-effect list.

08Common pitfallsFrequent interpretation and management errors.

01
Giving aromatase inhibition without considering ovarian function.
02
Ignoring tablet adherence when disease progresses.
03
Attributing focal bone pain to routine arthralgia.
04
Forgetting tamoxifen interactions and bleeding assessment.
05
Neglecting bone and metabolic prevention.
06
Stopping treatment without discussing alternatives.