Anastrozole

Anastrozole Tablets are indicated for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.

Anastrozole Tablets are indicated for the first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer.

Anastrozole Tablets are indicated for the treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy. Patients with ER-negative disease and patients who did not respond to previous tamoxifen therapy rarely responded to Anastrozole Tablets.

The dose of Anastrozole Tablets is one 1 mg tablet taken once a day. For patients with advanced breast cancer, Anastrozole Tablets should be continued until tumor progression. Anastrozole Tablets can be taken with or without food.

For adjuvant treatment of early breast cancer in postmenopausal women, the optimal duration of therapy is unknown. In the ATAC trial Anastrozole Tablets were administered for five years. [see Clinical Studies (14.1)]

No dosage adjustment is necessary for patients with renal impairment or for elderly patients. [see Use in Specific Populations (8.6)]

No changes in dose are recommended for patients with mild-to-moderate hepatic impairment. Anastrozole Tablets have not been studied in patients with severe hepatic impairment. [see Use in Specific Populations (8.7)]

Anastrozole Tablets may cause fetal harm when administered to a pregnant woman and offers no clinical benefit to premenopausal women with breast cancer. Anastrozole Tablets are contraindicated in women who are or may become pregnant. There are no adequate and well-controlled studies in pregnant women using Anastrozole Tablets. If Anastrozole Tablets are used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus or potential risk for loss of the pregnancy. [see Use in Specific Populations (8.1)]

Anastrozole Tablets are contraindicated in any patient who has shown a hypersensitivity reaction to the drug or to any of the excipients. Observed reactions include anaphylaxis, angioedema, and urticaria. [see Adverse Reactions (6.2)]

In women with pre-existing ischemic heart disease, an increased incidence of ischemic cardiovascular events was observed with Anastrozole Tablets in the ATAC trial (17% of patients on Anastrozole Tablets and 10% of patients on tamoxifen). Consider risk and benefits of Anastrozole Tablets therapy in patients with pre-existing ischemic heart disease. [see Adverse Reactions (6.1)]

Results from the ATAC trial bone substudy at 12 and 24 months demonstrated that patients receiving Anastrozole Tablets had a mean decrease in both lumbar spine and total hip bone mineral density (BMD) compared to baseline. Patients receiving tamoxifen had a mean increase in both lumbar spine and total hip BMD compared to baseline [see Adverse Reactions,(6.1) ].

During the ATAC trial, more patients receiving Anastrozole Tablets were reported to have elevated serum cholesterol compared to patients receiving tamoxifen (9% versus 3.5%, respectively) [see Adverse Reactions,(6.1) ].

Hepatobiliary events including increases in alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase have been reported (≥1% and <10%) and gamma-GT, bilirubin and hepatitis have been reported (≥0.1% and <1%) in patients receiving Anastrozole Tablets.

Anastrozole Tablets may also be associated with rash including cases of mucocutaneous disorders such as erythema multiforme and Stevens-Johnson syndrome.

Cases of allergic reactions including angioedema, urticaria and anaphylaxis have been reported in patients receiving Anastrozole Tablets. [see Contraindications (4.2)]

Trigger finger has been reported (>0.1% and <1%) in patients receiving Anastrozole Tablets.

Coadministration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%. However, the coadministration of anastrozole and tamoxifen did not affect the pharmacokinetics of tamoxifen or N-desmethyltamoxifen. At a median follow-up of 33 months, the combination of Anastrozole Tablets and tamoxifen did not demonstrate any efficacy benefit when compared with tamoxifen in all patients as well as in the hormone receptor-positive subpopulation. This treatment arm was discontinued from the trial. [see Clinical Studies (14.1)]. Based on clinical and pharmacokinetic results from the ATAC trial, tamoxifen should not be administered with anastrozole.

Estrogen-containing therapies should not be used with Anastrozole Tablets as they may diminish its pharmacological action.

In a study conducted in 16 male volunteers, anastrozole did not alter the exposure (as measured by C_max and AUC) and anticoagulant activity (as measured by prothrombin time, activated partial thromboplastin time, and thrombin time) of both R- and S-warfarin.

Based on in vitro and in vivo results, it is unlikely that co-administration of Anastrozole Tablets 1 mg will affect other drugs as a result inhibition of cytochrome P450 [see Clinical Pharmacology (12.3)].

It is not known if anastrozole is excreted in human milk. Because many drugs are excreted in human milk and because of the tumorigenicity shown for anastrozole in animal studies, or the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

The efficacy of Anastrozole Tablets in the treatment of pubertal gynecomastia in adolescent boys and in the treatment of precocious puberty in girls with McCune-Albright Syndrome has not been demonstrated.

Labeling describing clinical trials and pharmacokinetic studies of anastrozole in pubertal boys of adolescent age with gynecomastia and in girls with McCune-Albright Syndrome and progressive precocious is approved for AstraZeneca Pharmaceuticals LP's Arimidex^®. However, due to AstraZeneca Pharmaceuticals LP's marketing exclusivity rights, a description of those trials and studies is not approved for this Anastrozole Tablets labeling.

In studies 0030 and 0027 about 50% of patients were 65 or older. Patients ≥ 65 years of age had moderately better tumor response and time to tumor progression than patients < 65 years of age regardless of randomized treatment. In studies 0004 and 0005 50% of patients were 65 or older. Response rates and time to progression were similar for the over 65 and younger patients.

In the ATAC study 45% of patients were 65 years of age or older. The efficacy of Anastrozole Tablets compared to tamoxifen in patients who were 65 years or older (N=1413 for Anastrozole Tablets and N=1410 for tamoxifen, the hazard ratio for disease-free survival was 0.93 (95% CI: 0.80, 1.08)) was less than efficacy observed in patients who were less than 65 years of age (N=1712 for Anastrozole Tablets and N=1706 for tamoxifen, the hazard ratio for disease-free survival was 0.79 (95% CI: 0.67, 0.94)).

The pharmacokinetics of anastrozole are not affected by age.

Since only about 10% of anastrozole is excreted unchanged in the urine, the renal impairment does not influence the total body clearance. Dosage adjustment in patients with renal impairment is not necessary [see Dosage and Administration (2.1) and Clinical Pharmacology (12.3)].

The plasma anastrozole concentrations in the subjects with hepatic cirrhosis were within the range of concentrations seen in normal subjects across all clinical trials. Therefore, dosage adjustment is also not necessary in patients with stable hepatic cirrhosis. Anastrozole Tablets have not been studied in patients with severe hepatic impairment [see Dosage and Administration (2.2) and Clinical Pharmacology (12.3)].

The growth of many cancers of the breast is stimulated or maintained by estrogens. Treatment of breast cancer thought to be hormonally responsive (i.e., estrogen and/or progesterone receptor positive or receptor unknown) has included a variety of efforts to decrease estrogen levels (ovariectomy, adrenalectomy, hypophysectomy) or inhibit estrogen effects (antiestrogens and progestational agents). These interventions lead to decreased tumor mass or delayed progression of tumor growth in some women.

In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme.

Anastrozole is a potent and selective non-steroidal aromatase inhibitor. It significantly lowers serum estradiol concentrations and has no detectable effect on formation of adrenal corticosteroids or aldosterone.

A conventional carcinogenesis study in rats at doses of 1.0 to 25 mg/kg/day (about 10 to 243 times the daily maximum recommended human dose on a mg/m² basis) administered by oral gavage for up to 2 years revealed an increase in the incidence of hepatocellular adenoma and carcinoma and uterine stromal polyps in females and thyroid adenoma in males at the high dose. A dose related increase was observed in the incidence of ovarian and uterine hyperplasia in females. At 25 mg/kg/day, plasma AUC_{0-24 hr} levels in rats were 110 to 125 times higher than the level exhibited in postmenopausal volunteers at the recommended dose. A separate carcinogenicity study in mice at oral doses of 5 to 50 mg/kg/day (about 24 to 243 times the daily maximum recommended human dose on a mg/m² basis) for up to 2 years produced an increase in the incidence of benign ovarian stromal, epithelial and granulosa cell tumors at all dose levels. A dose related increase in the incidence of ovarian hyperplasia was also observed in female mice. These ovarian changes are considered to be rodent-specific effects of aromatase inhibition and are of questionable significance to humans. The incidence of lymphosarcoma was increased in males and females at the high dose. At 50 mg/kg/day, plasma AUC levels in mice were 35 to 40 times higher than the level exhibited in postmenopausal volunteers at the recommended dose.

Anastrozole Tablets have not been shown to be mutagenic in in vitro tests (Ames and E. coli bacterial tests, CHO-K1 gene mutation assay) or clastogenic either in vitro (chromosome aberrations in human lymphocytes) or in vivo (micronucleus test in rats).

Oral administration of anastrozole to female rats (from 2 weeks before mating to pregnancy day 7) produced significant incidence of infertility and reduced numbers of viable pregnancies at 1 mg/kg/day (about 10 times the recommended human dose on a mg/m² basis and 9 times higher than the AUC_{0-24 hr} found in postmenopausal volunteers at the recommended dose). Pre-implantation loss of ova or fetus was increased at doses equal to or greater than 0.02 mg/kg/day (about one-fifth the recommended human dose on a mg/m² basis). Recovery of fertility was observed following a 5-week non-dosing period which followed 3 weeks of dosing. It is not known whether these effects observed in female rats are indicative of impaired fertility in humans.

Multiple-dose studies in rats administered anastrozole for 6 months at doses equal to or greater than 1 mg/kg/day (which produced plasma anastrozole C_ssmax and AUC_{0-24 hr} that were 19 and 9 times higher than the respective values found in postmenopausal volunteers at the recommended dose) resulted in hypertrophy of the ovaries and the presence of follicular cysts. In addition, hyperplastic uteri were observed in 6-month studies in female dogs administered doses equal to or greater than 1 mg/kg/day (which produced plasma anastrozole C_ssmax and AUC_{0-24 hr} that were 22 times and 16 times higher than the respective values found in postmenopausal women at the recommended dose). It is not known whether these effects on the reproductive organs of animals are associated with impaired fertility in premenopausal women.

A multicenter, double-blind trial (ATAC) randomized 9,366 postmenopausal women with operable breast cancer to adjuvant treatment with Anastrozole Tablets 1 mg daily, tamoxifen 20 mg daily, or a combination of the two treatments for five years or until recurrence of the disease.

The primary endpoint of the trial was disease-free survival (i.e., time to occurrence of a distant or local recurrence, or contralateral breast cancer or death from any cause). Secondary endpoints of the trial included distant disease-free survival, the incidence of contralateral breast cancer and overall survival. At a median follow-up of 33 months, the combination of Anastrozole Tablets and tamoxifen did not demonstrate any efficacy benefit when compared with tamoxifen in all patients as well as in the hormone receptor positive subpopulation. This treatment arm was discontinued from the trial. Based on clinical and pharmacokinetic results from the ATAC trial, tamoxifen should not be administered with anastrozole. [see Drug Interactions (7.1)]

Demographic and other baseline characteristics were similar among the three treatment groups (see Table 7).

Patients in the two monotherapy arms of the ATAC trial were treated for a median of 60 months (5 years) and followed for a median of 68 months. Disease-free survival in the intent-to-treat population was statistically significantly improved [Hazard Ratio (HR) = 0.87, 95% CI: 0.78, 0.97, p=0.0127 in the Anastrozole Tablets arm compared to the tamoxifen arm. In the hormone receptor-positive subpopulation representing about 84% of the trial patients, disease-free survival was also statistically significantly improved (HR =0.83, 95% CI: 0.73, 0.94, p=0.0049) in the Anastrozole Tablets arm compared to the tamoxifen arm.

Figure 1 — Disease-Free Survival Kaplan Meier Survival Curve for all Patients Randomized to Anastrozole Tablets or Tamoxifen Monotherapy in the ATAC trial (Intent-to-Treat)

Figure

Figure 2 — Disease-free Survival for Hormone Receptor-Positive Subpopulation of Patients Randomized to Anastrozole Tablets or Tamoxifen Monotherapy in the ATAC Trial

Figure

The survival data with 68 months follow-up is presented in Table 9.

In the group of patients who had previous adjuvant chemotherapy (N=698 for Anastrozole Tablets and N=647 for tamoxifen), the hazard ratio for disease-free survival was 0.91 (95% CI: 0.73 to 1.13) in the Anastrozole Tablets arm compared to the tamoxifen arm.

The frequency of individual events in the intent-to-treat population and the hormone receptor-positive subpopulation are described in Table 8.

A summary of the study efficacy results is provided in Table 9.

Two double-blind, controlled clinical studies of similar design (0030, a North American study and 0027, a predominately European study) were conducted to assess the efficacy of Anastrozole Tablets compared with tamoxifen as first-line therapy for hormone receptor positive or hormone receptor unknown locally advanced or metastatic breast cancer in postmenopausal women. A total of 1021 patients between the ages of 30 and 92 years old were randomized to receive trial treatment. Patients were randomized to receive 1 mg of Anastrozole Tablets once daily or 20 mg of tamoxifen once daily. The primary end points for both trials were time to tumor progression, objective tumor response rate, and safety.

Demographics and other baseline characteristics, including patients who had measurable and no measurable disease, patients who were given previous adjuvant therapy, the site of metastatic disease and ethnic origin were similar for the two treatment groups for both trials. The following table summarizes the hormone receptor status at entry for all randomized patients in trials 0030 and 0027.

For the primary endpoints, trial 0030 showed that Anastrozole Tablets had a statistically significant advantage over tamoxifen (p=0.006) for time to tumor progression; objective tumor response rates were similar for Anastrozole Tablets and tamoxifen. Trial 0027 showed that Anastrozole Tablets and tamoxifen had similar objective tumor response rates and time to tumor progression (see Table 11 and Figure 3 and 4)

Table 11 below summarizes the results of trial 0030 and trial 0027 for the primary efficacy endpoints.

Figure 3 - Kaplan-Meier probability of time to disease progression for all randomized patients (intent-to-treat) in Trial 0030

Figure

Figure 4 - Kaplan-Meier probability of time to progression for all randomized patients (intent-to-treat) in Trial 0027

Figure

Results from the secondary endpoints were supportive of the results of the primary efficacy endpoints. There were too few deaths occurring across treatment groups of both trials to draw conclusions on overall survival differences.

Anastrozole was studied in two controlled clinical trials (0004, a North American study; 0005, a predominately European study) in postmenopausal women with advanced breast cancer who had disease progression following tamoxifen therapy for either advanced or early breast cancer. Some of the patients had also received previous cytotoxic treatment. Most patients were ER-positive; a smaller fraction were ER-unknown or ER-negative; the ER-negative patients were eligible only if they had had a positive response to tamoxifen. Eligible patients with measurable and non-measurable disease were randomized to receive either a single daily dose of 1 mg or 10 mg of Anastrozole Tablets or megestrol acetate 40 mg four times a day. The studies were double-blinded with respect to Anastrozole Tablets. Time to progression and objective response (only patients with measurable disease could be considered partial responders) rates were the primary efficacy variables. Objective response rates were calculated based on the Union Internationale Contre le Cancer (UICC) criteria. The rate of prolonged (more than 24 weeks) stable disease, the rate of progression, and survival were also calculated.

Both trials included over 375 patients; demographics and other baseline characteristics were similar for the three treatment groups in each trial. Patients in the 0005 trial had responded better to prior tamoxifen treatment. Of the patients entered who had prior tamoxifen therapy for advanced disease (58% in Trial 0004; 57% in Trial 0005), 18% of these patients in Trial 0004 and 42% in Trial 0005 were reported by the primary investigator to have responded. In Trial 0004, 81% of patients were ER-positive, 13% were ER-unknown, and 6% were ER-negative. In Trial 0005, 58% of patients were ER-positive, 37% were ER-unknown, and 5% were ER-negative. In Trial 0004, 62% of patients had measurable disease compared to 79% in Trial 0005. The sites of metastatic disease were similar among treatment groups for each trial. On average, 40% of the patients had soft tissue metastases; 60% had bone metastases; and 40% had visceral (15% liver) metastases.

Efficacy results from the two studies were similar as presented in Table 12. In both studies there were no significant differences between treatment arms with respect to any of the efficacy parameters listed in the table below.

When data from the two controlled trials are pooled, the objective response rates and median times to progression and death were similar for patients randomized to Anastrozole Tablets 1 mg and megestrol acetate. There is, in this data, no indication that Anastrozole Tablets 10 mg is superior to Anastrozole Tablets 1 mg.

Storage

Store at 20° to 25°C (68° to 77°F). Excursions permitted to 15° to 30°C (59° to 86°F). [See USP Controlled Room Temperature].

Patients should be advised that Anastrozole Tablets may cause fetal harm. They should also be advised that Anastrozole Tablets are not for use in premenopausal women; therefore, if they become pregnant they should stop taking Anastrozole Tablets and immediately contact their doctor.

Patients should be informed of the possibility of serious allergic reactions with swelling of the face, lips, tongue and/or throat (angioedema) which may cause difficulty in swallowing and/or breathing and to immediately report this to their doctor.

Patients with pre-existing ischemic heart disease should be informed that an increased incidence of cardiovascular events has been observed with Anastrozole Tablets use compared to tamoxifen use.

Patients should be informed that Anastrozole Tablets lowers the level of estrogen. This may lead to a loss of the mineral content of bones, which might decrease bone strength. A possible consequence of decreased mineral content of bones is an increase in the risk of fractures.

Patients should be informed that an increased level of cholesterol might be seen while receiving Anastrozole Tablets.

Patients should be advised not to take Anastrozole Tablets with Tamoxifen.