Hormone Therapy in Breast Cancer Treatment

What Are Hormones?

  • Hormones are chemical messengers that regulate body functions.

  • Oestrogen and progesterone are female sex hormones produced by:

    • Ovaries (in premenopausal women)

    • Fat and skin (in both men and women)

  • These hormones stimulate the growth of hormone-sensitive breast cancers.

What is Hormone Therapy?

  • Hormone therapy blocks or reduces hormone levels to slow or stop tumour growth.

  • Used only for hormone receptor-positive (HR+) breast cancers.

  • Types of breast cancer based on receptor status:

    • ER-positive (oestrogen receptor-positive)

    • PR-positive (progesterone receptor-positive)

    • HR-negative (no hormone receptors, does not respond to hormone therapy)

Types of Hormone Therapy for Breast Cancer

1. Blocking Ovarian Function (Ovarian Ablation)

  • Reduces oestrogen production in premenopausal women.

  • Methods:

    • Surgical removal of ovaries (oophorectomy)

    • Radiation therapy to disable ovarian function

    • GnRH agonists (e.g., Goserelin (Zoladex®))

2. Blocking Oestrogen Production (Aromatase Inhibitors)

  • Prevents conversion of androgens into oestrogen.

  • Used mainly in postmenopausal women.

  • Examples:

    • Anastrozole (Arimidex®)

    • Letrozole (Femara®)

    • Exemestane (Aromasin®)

3. Blocking Oestrogen's Effects (SERMs and Pure Anti-Oestrogens)

  • Selective Oestrogen Receptor Modulators (SERMs)

    • Tamoxifen (Nolvadex®) and Toremifene (Fareston®)

    • Blocks oestrogen receptors in breast tissue but acts as an agonist in bone and uterus.

  • Antioestrogens (e.g., Fulvestrant)

    • Pure antagonist; degrades oestrogen receptors.

How is Hormone Therapy Used?

1. Adjuvant Therapy (Early-Stage Cancer)

  • Given after surgery to reduce recurrence.

  • Tamoxifen or aromatase inhibitors used for 5+ years.

2. Treatment of Advanced or Metastatic Cancer

  • Used when cancer has spread or returned.

  • Combination with targeted therapy (e.g., Palbociclib + Letrozole).

3. Neoadjuvant Therapy (Before Surgery)

  • Used to shrink tumours before surgery.

  • Mainly in postmenopausal women.

Can Hormone Therapy Prevent Breast Cancer?

  • Used in high-risk women to reduce breast cancer risk.

  • Clinical trials show Tamoxifen, Raloxifene, and Aromatase Inhibitors can reduce breast cancer incidence.

Side Effects of Hormone Therapy

  • Common Side Effects:

    • Hot flashes, night sweats, vaginal dryness

  • Serious Side Effects:

    • Blood clots, stroke (Tamoxifen)

    • Bone loss, joint pain (Aromatase inhibitors)

Drug Interactions with Hormone Therapy

  • SSRIs (antidepressants) inhibit CYP2D6, reducing Tamoxifen metabolism.

  • Recommended alternatives: Sertraline, Venlafaxine.

Drug Table

Drug Name

Treatment Use

Mode of Action

Hormones Involved

Tamoxifen

Breast Cancer (HR+)

SERM; blocks oestrogen receptors

Oestrogen

Toremifene

Breast Cancer (HR+)

SERM; prevents oestrogen binding

Oestrogen

Anastrozole

Breast Cancer (HR+)

Aromatase inhibitor; reduces oestrogen production

Oestrogen

Letrozole

Breast Cancer (HR+)

Aromatase inhibitor; temporarily inactivates aromatase

Oestrogen

Exemestane

Breast Cancer (HR+)

Aromatase inhibitor; permanently inactivates aromatase

Oestrogen

Fulvestrant

Advanced Breast Cancer

Pure antioestrogen; degrades oestrogen receptors

Oestrogen

Goserelin

Ovarian Suppression

GnRH agonist; suppresses ovarian function

Oestrogen

Trastuzumab

HER2-Positive Breast Cancer

Monoclonal antibody targeting HER2 receptor

HER2

Palbociclib

Advanced Breast Cancer

CDK4/6 inhibitor; prevents cancer cell proliferation

Cyclin-Dependent Kinases

Key Takeaways

  • Hormone therapy is a cornerstone of breast cancer treatment.

  • Used to block oestrogen production or action.

  • Different strategies: ovarian suppression, aromatase inhibitors, SERMs, anti-oestrogens.

  • Personalized treatment based on hormone receptor status.

  • New combinations with targeted therapies improve outcomes.

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