Efficacy of tamoxifen ± aminoglutethimide in normal weight and overweight postmenopausal patients with hormone receptor-positive breast cancer: an analysis of 1509 patients of the ABCSG-06 trial.

BACKGROUND: There exists evidence that body mass index (BMI) impacts on the efficacy of aromatase inhibitors in patients with breast cancer. The relationship between BMI and the efficacy of tamoxifen is conflicting. We investigated the impact of BMI on the efficacy of single tamoxifen and tamoxifen plus an aromatase inhibitor in the well-defined prospective study population of the ABCSG-06 trial. METHODS: ABCSG-06 investigated the efficacy of tamoxifen vs tamoxifen plus aminoglutethimide in postmenopausal women with hormone receptor-positive breast cancer. Taking BMI at baseline, patients were classified as normal weight (BMI=18.5-24.9 kg m(-)(2)), overweight (BMI=25-29.9 kg m(-)(2)), and obese (30 kg m(-)(2)) according to WHO criteria. RESULTS: Overweight+obese patients had an increased risk for distant recurrences (hazard ratio (HR): 1.51; Cox P=0·018) and a worse overall survival (OS; HR: 1·49; Cox P=0·052) compared with normal weight patients. Analysing patients treated with single tamoxifen only, no difference between overweight+obese patients and normal weight patients regarding distant recurrence-free survival (HR: 1.35; Cox P=0·24) and OS (HR: 0.99; Cox P=0·97) could be observed. In contrast, in the group of patients treated with the combination of tamoxifen plus aminoglutethimide, overweight+obese patients had an increased risk for distant recurrences (1.67; Cox P=0·03) and a worse OS (1.47; Cox P=0·11) compared with normal weight patients. CONCLUSION: BMI impacts on the efficacy of aromatase inhibitor-based treatment but not single tamoxifen.

Randomized trial comparing aminoglutethimide with high-dose medroxyprogesterone acetate in therapy for advanced breast carcinoma.

A total of 218 postmenopausal patients were entered in a prospective randomized trial comparing aminoglutethimide (AG) and high-dose medroxyprogesterone acetate (MPA) as second-line hormonal therapy for advanced breast carcinoma. All responses were assessed by the criteria of the International Union Against Cancer. The response rates were 27% (29 of 106 patients) for AG and 31% (35 of 112) for MPA, but if stabilization of previously progressive disease is included, then the overall response rates were 51% (54 of 106) and 54% (61 of 112) for patients receiving AG or MPA, respectively. There was no difference in response to the two drugs at any site of disease, and the durations of response and survival were identical for the two drugs. The time to response was significantly shorter for patients treated with MPA (median, 8.7 wk) than for those treated with AG (median, 15.3 wk) (chi 2 = 9.96, 1 df, P = .0016). The percentage of patients experiencing toxic effects was equivalent in both arms, although the patterns and time courses of these effects were different.

Aminoglutethimide after tamoxifen therapy in advanced breast cancer: M. D. Anderson Hospital experience.

Forty-six patients with progressive metastatic disease following initial response to tamoxifen therapy were treated with aminoglutethimide. Three patients (6%) achieved complete remission, 15 patients (33%) had partial response, and eight patients (17%) had stable disease. Twenty patients (44%) had progressive disease. The most common side effects were transient skin rash, lethargy, or dizziness. In four patients (7%), treatment was discontinued because of undesirable side effects within the first 2 weeks of the study. These data show that aminoglutethimide is an effective agent following tamoxifen therapy.

Tamoxifen versus aminoglutethimide versus combined tamoxifen and aminoglutethimide in the treatment of advanced breast carcinoma.

In a control randomized cross-over trial, 117 patients with advanced breast cancer were treated initially either with tamoxifen (10 mg p.o. twice daily) or aminoglutethimide (250 mg p.o. 4 times daily) with hydrocortisone (20 mg twice daily). Patients failing to respond or relapsing were switched to the alternative treatment. Eighteen (30%) of the 60 patients initially treated with tamoxifen achieved an objective response, and 11 (18%) achieved stable disease. Seventeen (30%) of the 57 patients treated initially with aminoglutethimide achieved an objective response, and 13 (23%) achieved stable disease. Aminoglutethimide achieved a 35% objective response and a further 26% subjective bone pain relief in patients with bone metastases (overall, 61%) compared with a 17% objective response and a further 17% objective bone pain relief with tamoxifen (total, 34%). None of six premenopausal patients responded to aminoglutethimide compared with two of four responding to tamoxifen. The median response duration to aminoglutethimide was 16 months compared with 20 months for tamoxifen. Side effects for aminoglutethimide (including lethargy, rash, and depression) were more common than for tamoxifen, and 7% of aminoglutethimide-treated patients had to discontinue treatment because of these compared with 0% on tamoxifen. In cross-over studies, 6 of 12 tamoxifen responders who relapsed achieved a second response to aminoglutethimide (50%), as did 6 of 29 patients who initially failed to respond to tamoxifen (21%). In contrast, none of 11 patients relapsing after response to aminoglutethimide achieved a second response to tamoxifen; only 1 of 18 nonresponders to aminoglutethimide subsequently responded to tamoxifen (6%). In a subsequent study in which 62 patients were treated with combined tamoxifen and aminoglutethimide, the overall response rate of 37% was not significantly better than that for either agent used alone.

Randomized trial of aminoglutethimide versus tamoxifen in metastatic breast cancer.

We compared antiestrogen therapy (tamoxifen) with an estrogen suppression regimen (aminoglutethimide-hydrocortisone) in postmenopausal women with metastatic breast carcinoma. Fifteen of 39 patients (38%) who received tamoxifen experienced an objective tumor regression (3 complete, 12 partial remissions), whereas 13 of 36 women (36%) receiving aminoglutethimide responded (one complete remission, 12 partial remissions). The median duration of response was similar. The site of tumor involvement appears to be important in choosing between these hormonal treatments. Aminoglutethimide appears to offer a greater chance of response in patients with bone involvement.

Progress report on two clinical trials in women with advanced breast cancer. Trial I: tamoxifen versus tamoxifen plus aminoglutethimide. Trial II: aminoglutethimide in patients with prior tamoxifen exposure.

A progress report is presented on two on-going clinical trials in women with advanced breast cancer. In Trial I to date, 56 patients have been randomized to tamoxifen (TAM) alone or TAM plus aminoglutethimide (AG) (plus hydrocortisone). Patients failing TAM can then receive AG. The two groups are reasonably well balanced with respect to prior hormonal therapy exposure (TAM, 19%; TAM plus AG, 17%), age, disease-free interval, performance score, and estrogen receptor status. The TAM plus AG group has a higher incidence of visceral dominant disease (41 versus 26%) and prior chemotherapy exposure (41 versus 33%). Responses have been observed in 7 of 27 (26%) patients on TAM and 11 of 28 (39%) on TAM plus AG. Median times to treatment failure (defined as disease progression, unacceptable toxicity, or patient refusal) are 211 and 123 days, respectively (log-rank on time to treatment failure, p = 0.87). Toxicity is greater for TAM plus AG with a higher incidence of skin rash, lethargy, and dizziness. Thrombotic events were seen in one patient on TAM and two patients on TAM plus AG. One patient on TAM plus AG developed leukopenia and sepsis. The data are too preliminary for one to draw firm conclusions regarding relative efficacy. In TRial II to date, 35 patients with prior tamoxifen exposure have received AG. The mean number of prior systemic therapies is 3.2 (range, 1 to 7). The response rate is 20% and similar with (21%) or without (19%) prior chemotherapy exposure. The median time to treatment failure is 92 days. One patient developed leukopenia and sepsis. Additional patient accrual is necessary to allow characterization of potential efficacy within prognostically important subsets.

Phase II study of aminoglutethimide and medroxyprogesterone acetate in the treatment of patients with advanced breast cancer.

Forty-five women with far-advanced metastatic breast cancer were treated with a combination of aminoglutethimide (AG), 1000 mg p.o. daily, and medroxyprogesterone acetate (MPA), 1500 mg p.o. daily. Of 41 patients evaluable for treatment response, there were two complete responses, five partial remissions, 26 patients with minor tumor responses or no change, and eight nonresponders. Major side effects included those known for AG and MPA, i.e., impairment of mental functions, depressive syndromes, fatigue, ataxia, skin rash, changes in body weight, and transient increase of gamma-glutamyl-transferase. Most side effects disappeared spontaneously after 4 to 6 weeks of treatment. Plasma hormone measurements in 28 patients revealed no impairment of adrenocorticotropic hormone and cortisol levels. In conclusion, in the AG combination, it is feasible and safe to replace cortisol by MPA. Treatment results warrant further investigation of AG-MPA in patients with breast cancer of a more favorable prognosis.

Aminoglutethimide in the treatment of metastatic breast cancer.

Aminoglutethimide in combination with dexamethasone has been used in 44 patients with metastatic breast cancer who had prior response to hormonal manipulation and/or positive estrogen receptors. Objective tumor response (complete response plus partial response) has been achieved in 19 of 44 patients. Responses were seen in soft tissue, bone, and pleura. Eleven of 44 patients had stable disease, and 14 patients had progressive disease. The median duration of response was 8 months. Side effects were moderate, including lethargy, rash, fever, and Cushingoid facies. This treatment is well tolerated and is an effective hormone manipulation in postmenopausal patients with metastatic breast carcinoma.

Aminoglutethimide in the treatment of advanced postmenopausal breast cancer.

A group of 213 unselected postmenopausal women with advanced breast cancer were treated with aminoglutethimide, 250 mg 4 times a day, and hydrocortisone, 20 mg 2 times a day. Follow-up is 10 months to 4 years from the start of treatment. In 190 assessable patients, there were 6 complete responses (CR), 47 partial responses (PR), 25 stable disease (SD), and 3 mixed responses. Overall objective response rate was 28% and with SD was 41%. Median duration of objective response was 14 months. Objective response by site was: soft tissue, 31%; nodes, 27%; bone 23: liver, 22%; and lung, 16%. A further 32% of patients with bone deposits had SD, and 19 of 60 patients with progressive disease had pain relief. Years after menopause, age and tumor-free interval did not affect response rates. Thirty-eight % of patients responding to previous endocrine therapy responded to aminoglutethimide compared with 19% of patients who had progressed on previous endocrine therapy. A group of 213 patients were assessable for toxicity. Main side effects were drowsiness (33%), rash (23%), and nausea (15%). Eleven patients stopped treatment because of toxicity. Median survival from start of treatment was 28 months for PR-CR and for SD and 10 months for progressive disease (p less than 0.001). Median survival from first metastasis was 43 months for PR-CR, 40 months for SD (not significantly different), and 22 months for progressive disease (p less than 0.001). Aminoglutethimide is an effective endocrine therapy in advanced postmenopausal breast cancer, particularly for bone deposits. Disease stabilization is associated with symptomatic and survival benefit similar to CR-PR.

Use of aminoglutethimide as second-line endocrine therapy in metastatic breast cancer.

Sixty-five patients with advanced breast cancer, progressive despite prior endocrine therapy in all cases and prior chemotherapy in most cases, were treated with aminoglutethimide, 250 mg four times a day. At present, 52 are evaluable for response assessment, and of these 10 (19%) showed an overall objective response, major sites of response being soft tissue and lung. A further 12 patients (23%) had stable disease during aminoglutethimide therapy, while a total of 9 patients with bone metastases reported marked relief of pain without objective evidence of response. Forty-nine patients had received prior treatment with tamoxifen, and of the 10 tamoxifen responders 4 (40%) responded to subsequent aminoglutethimide, while of the 20 tamoxifen failures only 2 (10%) responded to subsequent aminoglutethimide. Aminoglutethimide was reasonably well tolerated, although 6 patients (0%) discontinued treatment because of intolerable side effects. Six of the 10 responding patients have subsequently relapsed, with a mean duration of response of 17 weeks, but 4 continued to respond at 24, 32, 55, and 111 weeks, respectively. The median survival from the start of aminoglutethimide therapy is in excess of 41 weeks for responders and 11 weeks for nonresponders, while the median survival from first relapse is 48 months for aminoglutethimide responders and 28 months for aminoglutethimide nonresponders. These results confirm that aminoglutethimide can offer a useful alternative form of endocrine therapy for advanced breast cancer, but the response rates obtained in heavily pretreated patients are inferior to those obtained when aminoglutethimide is used earlier in sequential treatment. For optimal results, particularly in terms of quality of life, aminoglutethimide should generally be used prior to chemotherapy.

Adjuvant aminoglutethimide therapy for postmenopausal patients with primary breast cancer: progress report.

A group of 122 postmenopausal patients with histologically proven node-positive primary breast cancer have been randomized to receive aminoglutethimide-hydrocortisone or placebo aminoglutethimide-placebo hydrocortisone for 2 years. Median follow-up is 17 months. In general, treatment was well tolerated, but 15 patients required a reduction in the dose of aminoglutethimide, and of these four patients were unable to continue therapy due to side effects. Primary staging, incidence of extensive node involvement, and estrogen receptor were similar in the treatment and control arms. Dehydroepiandrosterone sulfate (DHA-S) and estrone were measured in a subgroup of patients, and significant suppression of DHA-S levels throughout the duration of the treatment period as seen in patients receiving the active drug. No significant suppression of either DHA-S or estrone levels was seen in the controls. Patients were monitored for metastases by serial liver function tests, carcinoembryonic antigen, and chest X-rays, and of 26 relapsing patients only three patients were not detected by this screen. We conclude that adjuvant aminoglutethimide is moderately well tolerated. It is capable of suppressing DHA-S throughout 2 years of treatment. A further 280 patients will be entered into the study to assess the survival benefit for those taking aminoglutethimide-hydrocortisone.

Low-dose aminoglutethimide with and without hydrocortisone replacement as a first-line endocrine treatment in advanced breast cancer: a prospective randomized trial of the Italian Oncology Group for Clinical Research.

PURPOSE: A randomized study comparing low-dose aminoglutethimide (AG) with and without hydrocortisone (HC) was performed to investigate whether corticosteroid replacement contributes to the therapeutic effects of the drug administered as a front-line endocrine therapy in postmenopausal advanced breast cancer. PATIENTS AND METHODS: Postmenopausal patients who had not had prior endocrine therapy for advanced disease and with estrogen receptor (ER) or progesterone receptor (PgR) status positive or unknown were eligible. AG was administered at a dose of 250 mg twice a day orally (125 mg twice a day during the first month) with or without HC (20 mg twice a day orally). Seventy-nine and 74 patients were assessable for response on the AG plus HC arm and on the AG arm, respectively. The two treatment groups were well balanced and patients were largely untreated. Approximately 60% had not received any adjuvant treatment, and approximately 75% had not received any medical treatment after relapse. RESULTS: The overall responses (complete response [CR] plus partial response [PR]) were 44% and 41% for the AG plus HC and the AG arm, respectively, showing no significant difference. Time to progression (median, 8.1 and 6.3 months), duration of response (median, 15.8 and 13.7 months), and duration of survival (median, 34.2 and 36.3 months) were not significantly different between the two treatment arms. Side effects were infrequent and mild in both arms, with no significant differences. CONCLUSION: We conclude that half of the conventional daily dose of AG has optimal therapeutic activity as a front-line endocrine treatment of postmenopausal advanced breast cancer and that HC does not significantly contribute to the therapeutic effects.

Randomized trial of tamoxifen versus tamoxifen plus aminoglutethimide as adjuvant treatment in postmenopausal breast cancer patients with hormone receptor-positive disease: Austrian breast and colorectal cancer study group trial 6.

PURPOSE: To determine whether the addition of aminoglutethimide to tamoxifen is able to improve the outcome in postmenopausal patients with hormone receptor-positive, early-stage breast cancer. PATIENTS AND METHODS: A total of 2,021 postmenopausal women were randomly assigned to receive either tamoxifen for 5 years alone or tamoxifen in combination with aminoglutethimide (500 mg/d) for the first 2 years of treatment. Tamoxifen was administered at 40 mg/d for the first 2 years and at 20 mg/d for 3 years. RESULTS: All randomized and eligible patients were included in the analysis according to the intention-to-treat principle. After a median follow-up of 5.3 years, the 5-year disease-free survival in the aminoglutethimide plus tamoxifen group was 83.6% versus 83.7% in the monotherapy group (P =.89). The corresponding data for overall survival at 5 years were 91.4% and 91.2%, respectively (P =.74). More patients failed to complete combination treatment (13.7%) because of side effects as compared to tamoxifen alone (5.2%; P =.0001). CONCLUSION: Aminoglutethimide given for 2 years in addition to tamoxifen for 5 years does not improve the prognosis of postmenopausal patients with receptor-positive, lymph node-negative or lymph node-positive breast cancer.

Phase II study of suramin plus aminoglutethimide in two cohorts of patients with androgen-independent prostate cancer: simultaneous antiandrogen withdrawal and prior antiandrogen withdrawal.

Management of prostate cancer progression after failure of initial hormonal therapy is controversial. Recently, the activity of the simple discontinuation of antiandrogen therapy has been established by several groups, as well as the enhanced activity when combined with adrenal suppression (i.e., aminoglutethimide and hydrocortisone). Furthermore, suramin has generated considerable interest following reports of response rates ranging from 17 to 70%. More recently, suramin response rates of 18 and 22% have been reported when the potential confounding variables of flutamide withdrawal and hydrocortisone were prospectively controlled. On the basis of the activity of combining aminoglutethimide with flutamide withdrawal, we designed a protocol in which suramin was combined with aminoglutethimide in two cohorts of patients (those with simultaneous antiandrogen withdrawal compared to those who had previously discontinued antiandrogen therapy). Eighty-one evaluable patients were enrolled in this study between June 1992 and November 1994. Patients were a priori divided into two cohorts, those receiving prior antiandrogen withdrawal (n = 56) and those receiving simultaneous antiandrogen withdrawal (n = 25) at the time the patients were enrolled into the trial. For the group that discontinued antiandrogen prior to enrolling in therapy, the partial response rate (> 50% decline in PSA for > 4 weeks) was 14.2%, whereas the partial response was 44% for those patients who discontinued their antiandrogen at the time of starting suramin and aminoglutethimide. The median time to progression was 3.9 months in patients failing prior antiandrogen withdrawal and 5.5 months in those patients having concomitant antiandrogen withdrawal (P = 0.36 for the overall difference). The progression-free survival estimate at 1 year for patients having prior antiandrogen withdrawal was 19.8% [95% confidence interval (CI), 11-32.9%]. For those patients who experienced antiandrogen withdrawal simultaneous with the treatment, the progression-free survival estimates at 1 and 2 years were 27.1 (95% CI, 13.2-47.6%) and 4.5% (95% CI, 0.8-21.6%). The median survival time for those patients having prior antiandrogen withdrawal was 14.2 months, whereas the median survival was 21.9 months for those having concomitant antiandrogen withdrawal (P = 0.029 for the overall difference). In conclusion, the partial response rate of 44% for those who had concomitant flutamide withdrawal with adrenal suppression was consistent with that of other reports using a similar maneuver. Although this study was not randomized and thus we should not over-interpret the results, flutamide withdrawal plus adrenal suppression appears to have greater activity than flutamide withdrawal alone. Furthermore, these data suggest that suramin adds little to the response rate observed for other adrenal suppressive agents in the presence of antiandrogen withdrawal. This interpretation is in agreement with those studies controlling for adrenal suppression and flutamide withdrawal prior to suramin administration, which noted modest activity of short duration. Given that antiandrogen withdrawal is now accepted as an active maneuver for a subset of patients progressing after maximum androgen blockade, we propose that future trials attempting to maximize response rates incorporate this maneuver whenever possible into prospectively designed regimens.

Hypothyroidism associated with aminoglutethimide in patients with prostate cancer.

OBJECTIVE: The administration of aminoglutethimide and hydrocortisone is a second-line hormonal maneuver commonly prescribed for the treatment of metastatic prostate cancer. We determine the incidence of aminoglutethimide-induced primary hypothyroidism in an elderly population who have prostate cancer. DESIGN: Prospective evaluation. PATIENTS: Twenty-nine men with stage D2 prostate cancer who were treated at the National Cancer Institute, Bethesda, Md, in 1992. RESULTS: Clinical and biochemical evidence of hypothyroidism (thyrotropin levels greater than 10 mU/L) was noted in nine of 29 patients treated following the initiation of aminoglutethimide (250 mg four times daily). The elevation in thyrotropin and the clinical symptoms of hypothyroidism were reversed by the administration of levothyroxine (n = 4). CONCLUSION: Hypothyroidism should be included in the differential diagnosis of lethargy in elderly patients who are receiving aminoglutethimide for prostate cancer. Furthermore, patients who are receiving this agent at a dosage of 1000 mg/d or greater should have their serum thyrotropin levels monitored, and replacement therapy with levothyroxine should be initiated when abnormally elevated levels are noted.

Hepatic effects of aminoglutethimide: a model aromatic amine.

Primary aromatic amine drugs are structural alerts in drug development because of their association with a high incidence of idiosyncratic drug reactions (IDRs). If biomarkers could be found that predict IDR risk, it would have a major impact on drug development. Previous attempts to do this through screening of hepatic gene expression profiles in rodents treated with aromatic amine drugs found limited changes. Of the drugs studied, aminoglutethimide (AMG) induced the most changes, and this led to a more comprehensive study of its effects on the liver. Brown Norway rats treated with AMG for up to 14 days showed only a transient elevation of glutamate dehydrogenase. Pathway-specific PCR arrays found few AMG-induced gene changes associated with an immune response and, of these changes, the majority were involved with innate immunity such as Tlr2, Ticam2, CD14, and C3. AMG treatment also led to significant changes in the apoptosis and mitochondrial panel of genes. It was recently found that AMG does induce significant changes in the bone marrow of rats, and agranulocytosis is a common IDR caused by AMG. In contrast, liver injury is not a common IDR associated with AMG. Therefore, the liver may be able to effectively deal with AMG reactive metabolites, and changes observed in this study may be involved in adaptation. Myeloperoxidase is also known to be able to oxidize aromatic amines to reactive metabolites, and these observations suggest that metabolism outside of the liver may be important for the mechanism of aromatic amine-induced IDRs.

Use of aromatase inhibitors in breast carcinoma.

Aromatase, a cytochrome P-450 enzyme that catalyzes the conversion of androgens to estrogens, is the major mechanism of estrogen synthesis in the post-menopausal woman. We review some of the recent scientific advances which shed light on the biologic significance, physiology, expression and regulation of aromatase in breast tissue. Inhibition of aromatase, the terminal step in estrogen biosynthesis, provides a way of treating hormone-dependent breast cancer in older patients. Aminoglutethimide was the first widely used aromatase inhibitor but had several clinical drawbacks. Newer agents are considerably more selective, more potent, less toxic and easier to use in the clinical setting. This article reviews the clinical data supporting the use of the potent, oral competitive aromatase inhibitors anastrozole, letrozole and vorozole and the irreversible inhibitors 4-OH androstenedione and exemestane. The more potent compounds inhibit both peripheral and intra-tumoral aromatase. We discuss the evidence supporting the notion that aromatase inhibitors lack cross-resistance with antiestrogens and suggest that the newer, more potent compounds may have a particular application in breast cancer treatment in a setting of adaptive hypersensitivity to estrogens. Currently available aromatase inhibitors are safe and effective in the management of hormone-dependent breast cancer in post-menopausal women failing antiestrogen therapy and should now be used before progestational agents. There is abundant evidence to support testing these compounds as first-line hormonal therapy for metastatic breast cancer as well as part of adjuvant regimens in older patients and quite possibly in chemoprevention trials of breast cancer.

The psychotropic effects of inhibitors of steroid biosynthesis in depressed patients refractory to treatment.

Twenty patients, diagnosed as suffering from treatment-resistant major depression, were treated with one or more drugs that decrease corticosteroid biosynthesis. Nine were psychotic, 11 nonpsychotic. Seventeen completed the treatment (8 psychotic, 9 nonpsychotic); 13 responded (5 psychotic, 8 nonpsychotic; 11 responded completely (i.e., a drop in the Hamilton Depression Scale of at least 50%, to < or = 15), and 2 responded partially. The mean age of the responders (45.2 +/- 12.6 years) did not differ significantly from that of the nonresponders (48.7 +/- 12/3). Data were analyzed in the following categories; (1) the presence or absence of psychosis, (2) response or nonresponse to treatment, and (3) the drug(s) used (aminoglutethimide, ketoconazole, or a combination of either of these with metyrapone). The patients improved over time on the Hamilton Depression Scale independent of the medication used. Responders demonstrated improvement in mood, insomnia, anxiety, diurnal variation, paranoia and obsessive compulsiveness. Nonpsychotics responded better than psychotics.

Experience with aromatase inhibitors in the treatment of advanced breast cancer.

Inhibition of the aromatase enzyme system has become an established means of hormonal treatment for hormone-responsive advanced breast cancer. The widest clinical experience is with aminoglutethimide, which achieves around 30% objective remissions of metastatic disease for up to 1 year. Due to the sometimes serious side-effects of this drug, preclinical and clinical investigations have been undertaken and have yielded a number of steroidal and non-steroidal aromatase inhibitors that have been shown in early or mature clinical trials to give objective disease remissions similar to those with aminoglutethimide but with less toxicity. There is thus good reason to believe that newer aromatase inhibiting drugs will soon be available for routine use in patients with breast cancer. This paper summarizes our experience and reviews data from other groups.

Aromatase in breast cancer and the role of aminoglutethimide and other aromatase inhibitors.

Approximately one third of human breast carcinomas are hormone dependent and regress upon reduction of circulating estrogen levels. Traditional treatment strategies utilized surgical ablative methods to lower estrogen concentrations as treatment of breast cancer. Currently, investigative emphasis is focused upon development of highly specific antiestrogens and inhibitors of estrogen production. The enzyme, aromatase, as the terminal step in estrogen biosynthesis, is a logical target for blockade with potent and specific inhibitors. The earliest available aromatase antagonist, aminoglutethimide, suppresses estrogen production to the same extent as surgical ablation and is an effective treatment for breast cancer. Aminoglutethimide, however, blocks other cytochrome P-450-mediated steroid hydroxylations, requires concomitant glucocorticoid administration, and is associated with initial side effects. Several more specific inhibitors by destroying aromatase irreversibly as well as by competitive inhibition. One of these, 4-hydroxy-androstenedione, has been intensively studied in animals and is undergoing clinical trial. New data regarding these inhibitors further emphasize the key role of aromatase in estrogen production and the practical utility of blocking this enzyme.