Arimidex [Anastrozole] marketed by AstraZeneca Pharmaceuticals LP is a drugindicated in the treatment of adjuvant treatment [treatment following surgerywith or without radiation] of postmenopausal women with hormonereceptor-positive early breast cancer. It decreases the amount of estrogen inthe body.



It is chemically described as 1, 3-Benzenediacetonitrile, a, a, a', a'-Tetramethyl-5-(1H-1, 2, 4-triazol-1-ylmethyl).

Estrogen receptor positive breast cancer:

The estrogen receptor (ER) is a member of the nuclear hormone family ofintracellular receptors which is activated by the hormone 17β-estradiol(estrogen). The main function of the estrogen receptor is to act as a DNA binding transcription factor which wouldregulate gene expression. Apart from this function, the estrogen receptor alsohas additional functions independent of DNAbinding. There are two types of estrogen receptors, α and β, both encoded bydifferent genome [ESR1 on the sixth chromosome and ESR2 on the fourteenth chromosomerespectively] In 70% cases of breast cancer, over expression of the estrogenreceptor has been found, termed as ER positive. Researches postulate two thesesfor the occurrence of the same: - Binding of estrogen to the ER stimulatesproliferation of mammary cells, this result in increase in cell division and DNA replication leading to mutations. - It isthought that estrogen metabolism could lead to production of genotoxic wastes.

Both these processes could result in the disruption of cell cycle, apoptosisand DNA repair and therefore tumorformation. ERα is certainly associated with more differentiated tumors, whileevidence that ERβ is involved is controversial. Different versions of the ESR1gene have been identified (with single-nucleotide polymorphisms) and areassociated with different risks of developing breast cancer.

Particularly in postmenopausal women, the principal source of circulatingestrogen (primarily Estradiol) is conversion of adrenally-generatedandrostenedione to estrone by aromatase in peripheral tissues, with furtherconversion of estrone to estradiol. Many breast cancers also contain aromatase;the importance of tumor-generated estrogens is uncertain.

Arimidex [Anastrozole] is approved for the initial treatment ofpostmenopausal women with hormone receptor-positive or hormone receptor-unknownlocally advanced or metastatic breast cancer and for the treatment ofpostmenopausal women with advanced breast cancer that has progressed followingtreatment with tamoxifen. Patients with hormone receptor-negative disease andpatients who did not previously respond to tamoxifen therapy rarely respondedto Arimidex [Anastrozole]