Endocrine Therapy — Hormone Treatment for Cancer

Endocrine therapy refers to a group of medical treatments designed to interfere with the endocrine system's influence on cancer cell proliferation. Certain cancers, notably subtypes of breast, prostate, and endometrial tumours, rely on naturally occurring hormones such as oestrogen, progesterone, or androgens to fuel their survival and reproduction. These cancer cells express specific receptors that bind these hormones, triggering intracellular mechanisms that drive tumour enlargement.

This therapeutic strategy achieves its goals through multiple pharmacological mechanisms. Some drugs, such as selective oestrogen receptor modulators (e.g., tamoxifen) or androgen receptor antagonists (e.g., enzalutamide), physically attach to receptors and block natural hormones from binding. Other medicines, such as aromatase inhibitors (e.g., letrozole) or luteinising hormone-releasing hormone (LHRH) analogues, halt hormone production in tissues or reproductive organs. In selected clinical situations, surgical removal of hormone-producing glands—such as an oophorectomy or orchiectomy—may also be utilised.

For patients with hormone-receptor-positive tumours, endocrine therapy is one of the most effective and durable tools in oncology. Following surgery, adjuvant hormone therapy taken for five to ten years dramatically reduces the risk of cancer recurrence in early-stage breast and prostate cancers. In advanced or metastatic settings, it provides disease control over long periods with manageable side-effect profiles compared to cytotoxic chemotherapy. Understanding endocrine therapy empowers patients to actively participate in adherence strategies, manage long-term side effects like bone thinning, and make informed choices about survivorship care.

Before recommending endocrine therapy, pathologists test biopsy or surgical specimens using immunohistochemistry (IHC) to establish hormone receptor status. In breast cancer, samples are tested for oestrogen receptor (ER) and progesterone receptor (PR) expression; positive scores indicate suitability for endocrine drugs. In prostate cancer, androgen dependence is typical, though blood tests for prostate-specific antigen (PSA) and testosterone levels are used to monitor treatment response. Additional genomic assays (such as Oncotype DX or MammaPrint) help determine whether endocrine therapy alone is adequate or if chemotherapy is also required.

Endocrine therapy is most commonly employed in breast cancer that expresses oestrogen receptors (ER) or progesterone receptors (PR), which constitutes approximately 70 to 80 percent of all breast cancer diagnoses. It is equally central to treating prostate cancer, where androgen deprivation therapy (ADT) suppresses testosterone to stall tumour activity. Endocrine therapy is also applied in managing certain uterine (endometrial) cancers, ovarian granulosa cell tumours, and selected neuroendocrine tumours, where somatostatin analogues are used to control both tumour growth and hormone-related symptoms.

Starting endocrine therapy involves choosing a medication tailored to the patient's menopausal status, cancer stage, and overall health. Pre-menopausal women with breast cancer often receive tamoxifen, sometimes combined with ovarian suppression, while post-menopausal women typically receive aromatase inhibitors. Common side effects reflect hormone deprivation, including hot flushes, mood alterations, joint stiffness, and accelerated bone density loss. Consequently, bone mineral density scans and supportive measures like calcium, vitamin D, or bisphosphonates are frequently integrated into long-term management to protect skeletal health.