Mechanism of action
The elimination of estrogen-stimulating effects is a major factor in achieving tumour response when tumour tissue growth is dependent on the presence of estrogens.
In postmenopause, estrogens are mainly produced under the influence of the aromatase enzyme, which converts androgens synthesised by the adrenal glands, primarily androstenedione and testosterone, into estrone (E1) and estradiol (E2). Thus, suppression of estrogen synthesis in peripheral tissues and in the tissue of malignant neoplasms may be achieved by inhibition of the aromatase enzyme.
Letrozole is a non-steroidal aromatase inhibitor, has anti-estrogenic effect, selectively inhibiting aromatase by highly specific competitive binding to the subunit of this enzyme – heme of cytochrome P450. Blocks the synthesis of estrogen in all tissues.
- Early stages of invasive breast cancer whose cells have hormone receptors, in postmenopausal women, as adjuvant therapy.
- Early-stage invasive breast cancer in postmenopausal women after completion of standard adjuvant therapy with tamoxifen for 5 years as extended adjuvant therapy.
- Disseminated hormone-dependent breast cancer in postmenopausal women (first-line therapy).
- Disseminated breast cancer with recurrence or disease progression in postmenopausal women (natural or artificially induced) who have received prior anti-estrogen therapy.
- Hormone-dependent HER-2 negative breast cancer in postmenopausal women as neoadjuvant therapy in case of contraindications to chemotherapy and no need for emergency surgery.