Hormone therapy

What it is

Hormone therapy is a cancer treatment that slows or stops hormone-sensitive cancers by blocking hormones or their receptors, and it is used most often for breast and prostate cancers. The most important practical fact is that treatment commonly lasts years, not days or weeks, especially in early-stage hormone receptor-positive breast cancer and in many prostate cancer settings. You may also hear it called endocrine therapy, hormonal therapy, or hormonal cancer therapy.

Hormone therapy does not work for every cancer. It is mainly used when a cancer depends on hormones such as estrogen, progesterone, or testosterone to grow. In breast cancer, this usually means tumours that are estrogen-receptor positive and/or progesterone-receptor positive. In prostate cancer, treatment often aims to reduce androgen signaling because prostate cancer cells commonly rely on testosterone and related hormones.

Hormone therapy may be used:

1. Before surgery or radiation to shrink a tumour
2. After primary treatment to lower the risk of recurrence
3. For metastatic cancer to slow progression and reduce symptoms
4. With other treatments such as targeted therapy, radiation, or chemotherapy

A simple way to think about it is that hormone therapy either lowers the amount of hormone available to the cancer or blocks the cancer cell from responding to that hormone.

Cancer type	Common hormone target	Examples of treatment approaches
Breast cancer	Estrogen signaling	Tamoxifen, aromatase inhibitors, ovarian suppression
Prostate cancer	Androgen signaling	LHRH/GnRH agonists or antagonists, anti-androgens, orchiectomy
Some other cancers	Hormone-related pathways	Selected use in endometrial cancer or neuroendocrine settings

In India, the same broad principles are used as in international oncology practice, but the exact drug choice and duration depend on pathology reports, stage, menopausal status, access, cost, and tolerance of side effects.

How it works

Hormones are chemical messengers made by glands in the body. Some cancers use these signals to survive and divide. Hormone therapy interferes with that process in two main ways:

1. Reducing hormone production
2. Blocking hormone receptors or signaling inside the cancer cell

In breast cancer, tamoxifen blocks the estrogen receptor in breast tissue. Aromatase inhibitors such as letrozole, anastrozole, and exemestane lower estrogen production, mainly in postmenopausal patients. In premenopausal patients, doctors may also use ovarian suppression with medicines or surgery to reduce estrogen production.

In prostate cancer, treatment often lowers testosterone to very low levels using androgen deprivation therapy. This can be done with medicines that act on pituitary signaling, such as GnRH or LHRH agonists and antagonists, or with surgery to remove the testicles. Other drugs block the androgen receptor more directly.

Hormone therapy is different from chemotherapy. Chemotherapy attacks rapidly dividing cells more broadly, while hormone therapy is more selective and works only when the tumour biology shows hormone dependence.

Evidence and uses

Hormone therapy is a standard treatment for many hormone receptor-positive breast cancers and for many prostate cancers, with strong evidence that it can reduce recurrence risk, delay progression, and improve outcomes in the right patients. It is considered a mainstay of care in these cancers.

For breast cancer, endocrine therapy is commonly used after surgery in hormone receptor-positive disease. Depending on menopausal status and recurrence risk, treatment may continue for 5 years and sometimes longer. In metastatic breast cancer, endocrine therapy may be used alone or combined with targeted drugs, depending on tumour features and prior treatment.

For prostate cancer, androgen deprivation therapy may be used:

• with radiation for certain localised or locally advanced cancers
• for recurrent disease
• for metastatic disease
• to help control symptoms when cure is not possible

Hormone therapy is also used in some other cancer settings, but those uses are more selective. Examples include some endometrial cancers, thyroid cancer hormone suppression after thyroidectomy, corticosteroids in some blood cancers, and somatostatin analogues in neuroendocrine tumours. However, when people say "hormone therapy" in oncology, they usually mean treatment for breast or prostate cancer.

Response varies. Some cancers are highly sensitive at first and later become resistant. This is called endocrine resistance or hormone resistance. When that happens, doctors may switch drugs, add targeted therapy, or move to another treatment type.

Safety and interactions

Hormone therapy can be very effective, but side effects are common and are a major reason people stop treatment early. The side effects depend on the drug and the hormone pathway being blocked.

Common examples include:

• Hot flashes and sweats
• Joint or muscle pain
• Fatigue
• Low libido or sexual dysfunction
• Mood changes
• Vaginal dryness or menstrual changes
• Bone loss and higher fracture risk
• Weight or body-composition changes

Important drug-specific risks include:

Drug/group	Important risks or concerns
Tamoxifen	Blood clots, stroke risk, endometrial cancer risk, hot flashes
Aromatase inhibitors	Bone loss, fractures, joint pain, possible cholesterol effects
Androgen deprivation therapy	Bone loss, hot flashes, metabolic changes, sexual side effects, possible cardiovascular concerns
Anti-androgens	Liver effects with some agents, breast tenderness, fatigue

Interactions matter. For example, some antidepressants can interfere with how tamoxifen is activated in the body. Patients should tell their oncologist and pharmacist about all prescription drugs, over-the-counter medicines, and supplements. This includes Ayurvedic or herbal products, because some may affect liver enzymes or bleeding risk, even if evidence is limited.

Do not stop hormone therapy on your own because of side effects. Many problems can be managed with dose timing changes, supportive medicines, exercise, bone protection, or switching to another endocrine drug.

When to see a clinician

Contact your cancer team promptly if you have:

• new chest pain, shortness of breath, or one-sided leg swelling
• vaginal bleeding after menopause or unusual bleeding on tamoxifen
• severe bone pain or a suspected fracture
• fainting, severe dizziness, or palpitations
• major mood changes or inability to continue treatment
• troubling side effects that make you want to stop the medicine

Routine follow-up is important during hormone therapy. Doctors may monitor symptoms, menstrual status, bone health, blood pressure, lipids, glucose, and sometimes liver function, depending on the drug used. In breast cancer, bone density testing may be advised for people taking aromatase inhibitors or ovarian suppression. In prostate cancer, monitoring often includes PSA, symptoms, and assessment of bone and metabolic health.

Limitations and open questions

Hormone therapy only works when the cancer is hormone-sensitive, and even then it does not help every patient equally. Some tumours are resistant from the start, while others become resistant over time.

Another limitation is adherence. Because treatment often continues for years, side effects, cost, and treatment fatigue can reduce regular use. This can lower benefit in real-world care.

Research is ongoing on several questions:

1. Which patients benefit from longer treatment and which do not
2. How best to predict endocrine resistance
3. Which combinations with targeted therapy improve survival most
4. How to reduce long-term harms such as bone loss and metabolic effects

Evidence is strong for standard endocrine therapy in breast and prostate cancer, but the best sequence and duration can still vary by stage, biomarkers, age, menopausal status, and overall health. Decisions should be individualised with an oncologist rather than based on a general rule.