Hormonal Therapy in Oncology

Hormonal (endocrine) therapy treats cancers whose growth depends on hormone signalling — chiefly hormone-receptor-positive breast cancer and prostate cancer — by depriving the tumour of that signal. It works either by lowering hormone levels or by blocking the hormone receptor, and it is among the oldest forms of targeted systemic treatment, tracing to the demonstration that castration could control metastatic prostate cancer.

Definition

Hormonal therapy in oncology is the treatment of hormone-dependent cancers by interrupting hormonal signalling — either reducing the production of the driving hormone or antagonizing its receptor — to slow or arrest tumour growth.

Scope

This topic covers the rationale and mechanisms of endocrine treatment in oncology: receptor blockade, hormone-synthesis inhibition, the major drug classes, the role of receptor status as a predictive biomarker, and endocrine resistance. It is a conceptual reference and does not provide dosing or individualized treatment guidance.

Core questions

• Which cancers are hormone-dependent and why?
• How do receptor antagonists differ from hormone-synthesis inhibitors?
• How does receptor status predict benefit from endocrine therapy?
• Why does endocrine resistance develop over time?

Key concepts

• Hormone-receptor-positive cancer
• Estrogen receptor and androgen receptor
• Selective estrogen receptor modulators (e.g., tamoxifen)
• Aromatase inhibitors
• Androgen-deprivation therapy
• Receptor status as a predictive biomarker
• Endocrine resistance

Key theories

Hormone dependence of tumours

Certain cancers retain a dependence on the hormonal signals that drive their tissue of origin, so removing or blocking that hormone — as first shown when androgen deprivation controlled prostate cancer — can suppress tumour growth.

Mechanisms

Hormone-dependent tumours rely on receptor signalling to proliferate. Endocrine therapy interrupts this in two broad ways. Receptor-level approaches use antagonists or selective receptor modulators that bind the estrogen or androgen receptor and block its transcriptional activity. Ligand-depletion approaches lower circulating hormone: aromatase inhibitors reduce estrogen production in postmenopausal tissue, and androgen-deprivation strategies suppress testosterone in prostate cancer. Because benefit depends on the tumour expressing the relevant receptor, receptor status (e.g., estrogen-receptor positivity) functions as a predictive biomarker. Over time tumours may escape through receptor mutation, altered coregulators, or activation of bypass growth pathways, producing endocrine resistance.

Clinical relevance

Endocrine therapy is a mainstay of treatment for hormone-receptor-positive breast cancer and prostate cancer, often given over extended periods and combined with other modalities. Understanding its mechanisms supports appraisal of receptor-driven evidence and multidisciplinary communication. This entry explains principles and is not a guide to selecting agents, durations, or doses for any individual patient.

Evidence & guidelines

The benefit of endocrine therapy in receptor-positive early breast cancer is supported by large randomized-trial overviews, and its use is structured by tumour-specific guidelines (e.g., NCCN, ESMO). This reference summarizes the underlying principles rather than reproducing regimen- or duration-level recommendations.

History

Endocrine treatment of cancer began with Huggins and Hodges's 1941 demonstration that androgen deprivation by castration or estrogen could control metastatic prostate cancer, work later recognized with a Nobel Prize. The discovery of the estrogen receptor and the development of tamoxifen extended the approach to breast cancer, and randomized-trial overviews subsequently established the long-term survival benefit of endocrine therapy in receptor-positive disease.

Debates

Optimal duration of adjuvant endocrine therapy

Extending endocrine therapy beyond the traditional period can further reduce recurrence in some patients but adds cumulative toxicity; how long to treat, and for whom, remains a balance of benefit and harm.

Key figures

• Charles B. Huggins
• V. Craig Jordan
• Elwood Jensen
• Richard Peto

Seminal works

• huggins-hodges-1941
• jordan-2003
• ebctcg-2005

Frequently asked questions

Is hormonal therapy a form of chemotherapy?

No. Although both are systemic treatments, hormonal therapy works by blocking or lowering the hormones that drive certain cancers rather than by the broad cell-damaging mechanism of cytotoxic chemotherapy.

Why is receptor status checked before hormonal therapy?

Endocrine therapy only helps tumours that depend on hormone signalling, so testing whether a cancer expresses the relevant receptor predicts whether the treatment is likely to work.