Letrozole

Definition

Letrozole is a non-steroidal aromatase inhibitor used in the treatment of hormone-receptor positive breast cancer. It works by blocking the enzyme aromatase, which is responsible for the conversion of androgens to estrogens, thereby reducing estrogen levels in the body.

5 Must Know Facts For Your Next Test

1. Letrozole is approved for the treatment of postmenopausal women with hormone-receptor positive, early-stage breast cancer as adjuvant therapy following surgery and other initial treatment.
2. It is also used for the treatment of advanced or metastatic breast cancer in postmenopausal women whose cancer has progressed after treatment with other antiestrogen therapies.
3. Letrozole works by inhibiting the aromatase enzyme, which is responsible for the final step in the biosynthesis of estrogen from androgen precursors.
4. By reducing estrogen levels, letrozole deprives hormone-sensitive breast cancer cells of the growth-stimulating effects of estrogen, leading to reduced tumor growth and progression.
5. Letrozole has been shown to be more effective than tamoxifen, another commonly used antiestrogen therapy, in improving disease-free survival and overall survival in postmenopausal women with early-stage, hormone-receptor positive breast cancer.

Review Questions

• Explain how letrozole works to treat hormone-receptor positive breast cancer.
  • Letrozole is an aromatase inhibitor, which means it blocks the activity of the aromatase enzyme responsible for converting androgens to estrogens. By inhibiting aromatase, letrozole reduces the production of estrogen in the body. This is particularly important in the treatment of hormone-receptor positive breast cancer, where the growth and progression of the cancer is driven by the stimulatory effects of estrogen. By depriving the cancer cells of estrogen, letrozole can effectively slow or stop the growth of the tumor, leading to improved outcomes for patients.
• Compare and contrast the use of letrozole and tamoxifen in the treatment of early-stage, hormone-receptor positive breast cancer.
  • Letrozole and tamoxifen are both used in the treatment of hormone-receptor positive breast cancer, but they work through different mechanisms. Tamoxifen is a selective estrogen receptor modulator (SERM) that blocks the action of estrogen on breast cancer cells, while letrozole is an aromatase inhibitor that reduces the overall production of estrogen in the body. Studies have shown that letrozole is more effective than tamoxifen in improving disease-free survival and overall survival in postmenopausal women with early-stage, hormone-receptor positive breast cancer. This is likely due to the more complete estrogen deprivation achieved with letrozole, as it targets the source of estrogen production rather than just blocking its effects.
• Discuss the role of estrogen deprivation in the mechanism of action of letrozole and its implications for the treatment of hormone-receptor positive breast cancer.
  • The key mechanism of action of letrozole in the treatment of hormone-receptor positive breast cancer is the reduction of estrogen levels in the body. By inhibiting the aromatase enzyme, letrozole blocks the conversion of androgens to estrogens, leading to a significant decrease in circulating estrogen. This estrogen deprivation is crucial, as estrogen is the primary driver of tumor growth and progression in hormone-receptor positive breast cancer. By depriving the cancer cells of this growth-stimulating hormone, letrozole can effectively slow or stop the growth of the tumor, ultimately improving outcomes for patients. The ability of letrozole to achieve more complete estrogen deprivation compared to other antiestrogen therapies, such as tamoxifen, is a key factor in its superior efficacy in the treatment of early-stage, hormone-receptor positive breast cancer.

Related terms

Aromatase: An enzyme responsible for the conversion of androgens (such as testosterone) to estrogens (such as estradiol) in various tissues, including the ovaries, adrenal glands, and peripheral fat.

Hormone-Receptor Positive Breast Cancer: A type of breast cancer in which the cancer cells have receptors for the hormones estrogen and/or progesterone, and the growth of the cancer is stimulated by these hormones.

Estrogen Deprivation: The reduction or elimination of estrogen levels in the body, which can be achieved through the use of aromatase inhibitors like letrozole.