Anastrozole: An effective drug to treat Breast Cancer

Anastrozole: An effective drug to treat Breast Cancer

Currently, breast cancer is recognized as one of the largest epidemiological problems in females. This invasive cancer affects about 2.1 million females each year and is the principal cause of cancer-associated mortality among females. Estrogen, a primary female sex hormone, plays a fundamental role in the growth and progression of hormone-dependent tumours of the breast.

Some breast carcinomas are known to be estrogen-receptor positive i.e. the sex hormone estrogen assists in the tumour's growth and progression. Impairing the activity of estrogen through suppressing estrogen action or by reducing estrogen production is a pivotal therapeutic approach for fighting breast cancer.

Aromatase inhibitors have potentially emerged as an alternative first-line endocrine therapy for managing hormone-sensitive breast cancer in postmenopausal women. One such potent aromatase inhibitor is Anastrozole. It has displayed promising results in combating breast cancer by decreasing the availability of estrogen. It is indeed a boon for postmenopausal women who are at a raised risk of developing breast carcinoma.

Let's explore how Anastrozole can help to prevent or treat breast cancer:

  • What is Anastrozole?
  • Mechanism of action of Anastrozole
  • Clinical use of Anastrozole
  • Dosage and administration
  • Contraindications of Anastrozole
  • Clinical evidence of anti-cancer activity
  • Conclusion

What is Anastrozole?

Anastrozole is a non-steroidal third-generation inhibitor of aromatase indicated for treating postmenopausal women suffering from breast cancer.

Mechanism of action of Anastrozole

Anastrozole works by lowering the availability of estrogen by inhibiting the aromatase enzyme.

Clinical use of Anastrozole

Anastrozole, a highly competitive and selective inhibitor of aromatase, has been granted approval by the United States Food and Drug Administration (USFDA) as:

  • Adjuvant therapy for managing postmenopausal females diagnosed with hormone receptor-positive early-stage breast carcinoma
  • First-line management of postmenopausal females diagnosed with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast carcinoma.
  • Management of advanced-stage breast cancer in postmenopausal females who experience tumour progression despite treatment with tamoxifen.

Dosage and administration of Anastrozole

The suggested dose of Anastrozole to treat breast cancer is one 1 mg tablet taken once daily. In the following patients, the dose of Anastrozole should not be altered.

  • elderly patients
  • patients with mild to moderate liver impairment
  • patients with renal impairment

Contraindications of Anastrozole

The use of Anastrozole is contraindicated in:

  • Pregnancy and premenopausal women

This drug may potentially harm the fetus when given to a pregnant female, and yields no clinical benefit to premenopausal females suffering from breast cancer.

  • Hypersensitivity

This drug should be avoided in any patient who has demonstrated a hypersensitivity reaction to this drug

Clinical evidence of anti-cancer activity

In a study reporting blinded long-term post-treatment follow-up results for the International Breast Cancer Intervention Study (IBIS)-II trial, Anastrozole demonstrated long-term efficacy in preventing breast cancer (both invasive and ductal carcinoma in situ) in high-risk postmenopausal women. No novel late side-effects were witnessed.

A phase 3 ATAC (Arimidex, Tamoxifen Alone or in Combination) trial compared anastrozole with tamoxifen for five years in 9366 postmenopausal females with localized early estrogen receptor-positive breast tumour. In this trial, Anastrozole demonstrated superiority to tamoxifen as it:

  • prolonged disease-free survival
  • raised time to recurrence
  • reduced distant metastases
  • prevented contralateral breast cancers
  • Anastrozole was also linked with fewer side-effects compared to tamoxifen

In the combined analyses of two large multicenter studies, involving 1021 participants, anastrozole was found to be superior to tamoxifen for the first-line therapy of advanced breast carcinoma in postmenopausal females whose tumours were either receptor-positive or of unknown receptor status. In patients whose tumours were estrogen receptor and/or progesterone receptor-positive, anastrozole therapy provided a favourable efficacy–toxicity ratio benefit over tamoxifen.

In two international, phase III, randomized trials (0027 and 0030), anastrozole, as a second-line
therapy demonstrated superior efficacy to megestrol acetate in terms of the overall clinical benefit and time to disease progression in postmenopausal females suffering from estrogen receptor and/or progesterone receptor-positive advanced breast cancer. Compared to megestrol acetate, anastrozole was showed good tolerability.

In N-methyl-N-nitrosourea-induced premenopausal mammary carcinogenesis in female rats, 0.5 mg/kg anastrozole was found to lower tumour incidence by 40% and tumour frequency by 57%, as well as raise the latency period by 10 days compared to the control group rats.

Another study [Study of Tamoxifen or Arimidex, combined with Goserelin acetate, to compare Efficacy and safety (STAGE)] indicated that the combination of anastrozole plus goserelin may represent an alternative neoadjuvant therapy choice for premenopausal females suffering from estrogen receptor-positive early-stage breast cancer. In this study, the combo of Anastrozole and goserelin illustrated higher efficacy and better risk-benefit profile compared to tamoxifen plus goserelin.


In high-risk postmenopausal women, the use of Anastrozole has been supported for breast cancer prevention by the National Institute for Health and Care Excellence in the United Kingdom, and also by the US Preventive Services Task Force in the United States of America.

Anastrozole has become a vital drug of choice for postmenopausal breast cancer patients, as it is associated with a stronger therapeutic activity and better tolerability compared to other anti-cancer agents. However, the identification of women at elevated risk of early symptoms of estrogen depletion and their management remains an important challenge.

Anastrozole is available as Armocad Tablets.

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