Aminoglutethimide in advanced breast cancer: clinical results of a French multicenter randomized trial comparing 500 mg and 1 g/day

Update on aromatase inhibitors in breast cancer

PURPOSE OF REVIEW

Hormonal treatment is one of the cornerstones of management for breast cancer. For many years, tamoxifen represented the gold standard. The development of aromatase inhibitors has, however, challenged the primary role of tamoxifen. Randomized studies evaluating the role of aromatase inhibitors in both the metastatic and adjuvant settings, in postmenopausal women, have been conducted. This article describes the most recent available data for these trials.

RECENT FINDINGS

The efficacy of aromatase inhibitors for metastatic disease is well established and has not changed recently. Multiple adjuvant aromatase inhibitor trials have been completed and published or presented. These trials vary in the timing of aromatase inhibitor administration, but all show statistically significant reductions in breast-cancer recurrence. An improvement in overall survival has not been observed to date. Tolerability is improved with aromatase inhibitors, the major concern with the use of aromatase inhibitors being the development of osteoporosis and bone fractures.

SUMMARY

Aromatase inhibitors are consistently showing improved efficacy and tolerability to tamoxifen for both early and advanced breast cancer. Optimal therapy for postmenopausal women should include an aromatase inhibitor. The optimal sequence of aromatase inhibitors and tamoxifen for adjuvant therapy is still, however, under investigation.

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.

Letrozole, a new oral aromatase inhibitor: randomised trial comparing 2.5 mg daily, 0.5 mg daily and aminoglutethimide in postmenopausal women with advanced breast cancer. Letrozole International Trial Group (AR/BC3)

BACKGROUND

The study compares letrozole and aminoglutethimide (AG), a standard therapy for postmenopausal women with advanced breast cancer, previously treated with antioestrogens.

PATIENTS AND METHODS

555 women were randomly assigned letrozole 2.5 mg once daily (n = 185), letrozole 0.5 mg once daily (n = 192) or aminoglutethimide 250 mg twice daily with corticosteroid support (n = 178) in an open-label, multicentre trial. The primary endpoint was objective response rate (ORR), with time events as secondary. ORR was analysed nine months after enrollment of the last patient, while survival was analysed 15 months after the last patient was enrolled. We report the results of these analyses plus an extended period of observation (covering a total duration of approximately 45 months) to determine the duration of response and clinical benefit.

RESULTS

Overall objective response rates (complete + partial) of 19.5%, 16.7% and 12.4% were seen for letrozole 2.5 mg, 0.5 mg and AG respectively. Median duration of response and stable disease was longest for letrozole 2.5 mg (21 months) compared with letrozole 0.5 mg (18 months) and AG (14 months). Letrozole 2.5 mg was superior to AG in time to progression, time to treatment failure and overall survival. Treatment-related adverse events occurred in fewer patients on letrozole (33%) than on AG (46%). Transient nausea was the most frequent event with letrozole (7% on 0.5 mg, 10% on 2.5 mg, 10% on AG), rash with AG (11%, 1% on 0.5 mg, 3% on 2.5 mg letrozole).

CONCLUSIONS

Letrozole 2.5 mg offers longer disease control than aminoglutethimide and letrozole 0.5 mg in the treatment of postmenopausal women with advanced breast cancer, previously treated with anti-oestrogens.

A randomised trial comparing two doses of the new selective aromatase inhibitor anastrozole (Arimidex) with megestrol acetate in postmenopausal patients with advanced breast cancer

The aim of this study was to compare the efficacy and tolerability of the new aromatase inhibitor 'ARIMIDEX' (anastrozole) with megestrol acetate in the treatment of advanced breast cancer in postmenopausal women. Anastrozole is a new potent and highly selective non-steroidal aromatase inhibitor. We conducted a prospective randomised trial comparing two doses of anastrozole (1 and 10 mg orally once daily) with megestrol acetate (40 mg orally four times daily) in postmenopausal patients with advanced breast cancer who progressed after prior tamoxifen therapy. All patients were analysed for efficacy as randomised (intention to treat) and for tolerability as per treatment received. Of the 378 patients who entered the study, 135 were randomised to anastrozole 1 mg, 118 to anastrozole 10 mg, and 125 patients to megestrol acetate. After a median follow-up of 192 days, response rate which included complete response, partial response and patients who had disease stabilisation for 6 months or more was 34% for anastrozole 1 mg, 33.9% for anastrozole 10 mg and 32.8% for megestrol acetate. There were no statistically significant differences between either dose of anastrozole and megestrol acetate in terms of objective response rate, time to objective progression of disease or time to treatment failure. The three treatments were generally well tolerated, but more patients on megestrol acetate reported weight gain, oedema and dyspnoea as adverse events while more patients on anastrozole reported gastro-intestinal disorders, usually in the form of mild transient nausea. Patients on anastrozole did not report higher incidences of oestrogen withdrawal symptoms. Anastrozole is an effective and well tolerated treatment for postmenopausal patients with advanced breast cancer. The higher 10 mg dose did not result in additional clinical benefit, but was well tolerated reflecting the good therapeutic margin with anastrozole. Based on this data, anastrozole 1 mg should be the recommended therapeutic dose.

Adrenal effects of low-dose aminoglutethimide when used alone in postmenopausal women with advanced breast cancer

Aminoglutethimide (Ag) is a potent aromatase-enzyme inhibitor used in the treatment of patients with breast cancer. In the past, it has been administered in doses of 1,000 mg/d (usually with 40 mg hydrocortisone). At these dose levels, the drug also affects multiple cytochrome P-450 enzymes, including enzymes for adrenal steroid biosynthesis. Recently, lower-dose regimens (500 mg/d) of Ag have been found to be just as effective for breast cancer therapy, but less toxic than the higher conventional dose. There is limited information on the adrenal effects at the lower dosages, and it is not known whether these effects are clinically significant. We measured basal and synthetic corticotropin (Cortrosyn)-stimulated levels of adrenal steroids in postmenopausal breast cancer patients before and during treatment with low-dose Ag (500 mg/d) administered without a glucocorticoid preparation. Basal levels of progesterone, 17-OH progesterone, and 11-deoxycortisol were higher after 2 months' treatment (P < .01). After ACTH injection, peak levels of progesterone and 17-OH progesterone were higher (P < .01), but in contrast, peak levels of 18-OH corticosterone were lower during treatment (P < .02). Basal and peak levels of cortisol, aldosterone, and all other adrenal steroids were unchanged during treatment. We conclude that low-dose Ag treatment leads to partial inhibition of the 21-hydroxylase, 11-hydroxylase, and 18-hydroxylase adrenal enzymes. Since cortisol and aldosterone secretion remained normal with minimal shunting to or accumulation of adrenal androgen compounds, we believe that the mild inhibition was compensated for by further endogenous ACTH stimulation.

First generation aromatase inhibitors--aminoglutethimide and testololactone

Aminoglutethimide and testololactone may be considered the first generation aromatase inhibitors for the endocrine treatment of breast carcinoma. Initially, both of these agents were designed and used clinically based on different concepts of their mechanisms of action. Only later were they both demonstrated to inhibit aromatase. Curiously, testololactone was earlier and more widely used than aminoglutethimide in treating advanced breast carcinoma. The discovery of the peripheral aromatase inhibition as the proper mechanism of action was delayed for both the agents but was relatively more timely for aminoglutethimide. Paradoxically, the clinical use of testololactone has become already obsolete since its true mechanism of action was discovered. Aminoglutethimide is still the most widely used aromatase inhibitor in treating advanced breast carcinoma. Due to the initial misinterpretation of its mechanism of action, aminoglutethimide was used for a long time at a relative high daily dose, always combined with hydrocortisone. Subsequent phase II and then randomized phase III studies demonstrated an equivalent efficacy using half (500 mg) of the previous conventional daily dose (1000 mg), with hydrocortisone. Very recently, a randomized clinical trial demonstrated that administering this lower dose without hydrocortisone did not significantly decrease the clinical efficacy. By decreasing the dose of aminoglutethimide, the incidence of side effects has been reduced. So, the last paradoxical aspect of the aminoglutethimide story is that this agent seemed initially very toxic but finally, with the new schedules, shows a very low toxicity profile, especially after the first few weeks of treatment.

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.

Aminoglutethimide (AG) and hydrocortisone (HC) in bone metastases: a retrospective study

The response rate in bone metastases in 57 patients treated with aminoglutethimide and hydrocortisone was retrospectively assessed. All the X-rays were reviewed by two senior radiologists. A response was observed in 23% of the patients, a stabilization in 32%. The survival was not different whether a response or stabilization was observed. Conversely, survival was significantly worse in patients who experienced a progressive disease.

Systemic therapy of advanced breast cancer

Many cytotoxic agents have demonstrated activity in advanced breast cancer, the more active agents being cyclophosphamide and the anthracyclines doxorubicin and epirubicin. Combinations of drugs are generally superior to single agents in terms of response rate, duration of response and survival. The treatment of advanced breast cancer can be continued either until treatment failure, or for a limited time from either initiation of therapy or from the observation of complete response. Although these are issues of significant concern, data from randomised trials are limited, and so the question of optimal treatment duration remains open. Randomised trials comparing regimens that differ by a dose intensity factor of less than 2 have failed to demonstrate significant differences in efficacy between the dose levels. With higher doses, as applied in combination with colony-stimulating factors and bone marrow transplantation, response rates seem to increase, but whether this translates into improved survival has not yet been answered by the results of randomised trials. Approximately 30% of patients respond to endocrine therapy. From the results of randomised trials, which have compared the efficacies and toxicities of different endocrine modalities including combined endocrine therapy, single-agent tamoxifen is generally considered as the preferred first-line treatment, leaving progestins and aromatase inhibitors as alternatives for second-line endocrine therapy in responders. In the majority of trials, chemotherapy combined with endocrine therapy has given improved response rates compared with chemotherapy alone, but the differences have not generally been translated into prolonged survival with combined modalities. This gives rise to the question of the optimal sequence of chemotherapy and endocrine therapy, a subject needing further evaluation in future trials.

Aminoglutethimide in advanced breast cancer: plasma levels and clinical results after low and high doses

Drug plasma levels, metabolism data and clinical results were evaluated after the daily administration of either 500 or 1,000 mg aminoglutethimide (AG, Orimeten, Ciba-Geigy) plus hydrocortisone acetate (20 mg b. i. d.). A total of 34 patients with advanced breast cancer entered the study: 17 were given 1,000 mg/day and 17 received 500 mg/day for at least 3 months. A novel HPLC method was developed to determine the levels of AG and its known metabolites [N-acetyl-AG (NAG), formyl-AG, nitroglutethimide, hydroxy-AG] in the biological samples. AG plasma concentration was significantly higher during the 1,000-mg/day regimen. NAG was the only metabolite observed in plasma, always occurring at concentrations lower than those of the parent drug. The ratios between NAG and AG levels distinguish two statistically different groups of patients. Irrespective of the dose, a partial response was observed in 44% of the patients; no change in 32% of cases; and progressive disease had an incidence of 24%. The probability of response was not dependent on the drug AUC or on the NAG/AG ratio and did not significantly depend on previous hormone treatment. Neither the plasmatic level of the AG or metabolite concentrations nor the NAG/AG ratio seemed to affect the incidence of side effects.

Second line endocrine treatment of postmenopausal advanced breast cancer. Preliminary endocrine results of a 5-arm randomized phase II trial of medium vs low dose aminoglutethimide, with or without hydrocortisone vs hydrocortisone alone (EORTC 10861)

The supposed mechanism of action of aminoglutethimide (AG), medical adrenalectomy, has been challenged. AG is now considered to act as an inhibitor of the aromatization of mainly adrenal androgens to estrogens in peripheral tissues and/or breast cancer itself. To further establish the AG dose required to sufficiently reduce estrogen levels in plasma and the possible role of hydrocortisone (HC) in combination with AG or by itself, postmenopausal advanced breast cancer patients received AG low (125 mg bid) or medium (250 mg bid) dose alone or combined with HC (20 mg bid) or HC alone (20 mg bid). Preliminary hormonal data show a similar reduction of serum estrone and estrone sulphate by at least some 50% at 8 wk in all treatment groups. At 6 months these effects persist except for patients treated with HC alone. In the latter a normalization of estrone levels is observed with effective suppression of adrenal androgen precursors, suggesting increased aromatase activity with prolonged glucocorticoid treatment.

Phase II study of low dose aminoglutethimide 250 mg/day plus hydrocortisone in advanced postmenopausal breast cancer

Low dose aminoglutethimide 125 mg twice daily plus hydrocortisone 20 mg twice daily was shown to produce oestrogen and androgen suppression in postmenopausal women. A phase II study was carried out in 101 patients with advanced postmenopausal breast cancer. Objective response rates were 4% CR and 21% PR. Fourteen per cent had disease stabilization for more than 6 months (SD). Soft tissue sites showed the best response. Responses occurred in previous tamoxifen failures (28%) including SD. Toxicity was less than reported for higher dose regimens or low dose aminoglutethimide without hydrocortisone, particularly nausea and drowsiness. Survival from first relapse and start of therapy was not significantly different between PR and SD. This dosage regimen appears of comparable efficacy to previously reported higher dosage regimens with reduced toxicity compared to low dose regimens without hydrocortisone.

Low dose aminoglutethimide without hydrocortisone for the treatment of advanced postmenopausal breast cancer

One hundred and one postmenopausal patients with advanced breast cancer were enrolled in a randomized phase II clinical trial to investigate the clinical and hormonal response to aminoglutethimide administered at daily doses of 2 x 125 mg, 3 x 125 mg or 2 x 250 mg, with no addition of hydrocortisone. Among 71 evaluable patients 25% showed objective tumor response (three complete, 15 partial), at all three dose levels and irrespective of the major tumor site. Previous treatment with Tamoxifen had been successful in 75%. Out of the 18 responding patients 10 had estrogen receptor positive, four had estrogen receptor negative tumors; the receptor status was unknown in four other patients. Progression-free interval was more than 700 days in 50% of the responders. Drowsiness caused early drug withdrawal in one patient. Side-effects were very mild, comparing favorably with standard therapy of 250 mg aminoglutethimide q.i.d. plus hydrocortisone. Plasma estrogen levels were reduced by all doses to the same 50% or less as in patients on standard treatment. In nine out of 27 patients a further decrease of estrone levels could be monitored with clinically improved results in five. Plasma cortisol and mineralocorticoids remained normal throughout more than 6 months. The original role of hydrocortisone administration to suppress a reflex rise of ATH in 'medical adrenalectomy' with standard dose aminoglutethimide is no longer tenable. Further phase III comparative clinical results pending, low dose aminoglutethimide as an aromatase inhibitor may at present be considered as an appropriate second-line endocrine treatment with low toxicity and expense.

Low-dose aminoglutethimide plus steroid replacement in advanced breast cancer patients resistant to conventional therapies

In an attempt to define the activity and toxicity of low-dose aminoglutethimide plus steroid replacement in advanced breast cancer, we treated 40 patients with aminoglutethimide 500 mg/day + hydrocortisone 50 mg/day. Previous treatment consisted of additive hormones in 29 patients, oophorectomy in 8, and chemotherapy in 32. Among the 37 patients evaluable for response and toxicity, 5 objective responses (16.2%) and 20 stable diseases (54%) were noted. Toxicity, absent in 23 patients (62.1%) and mild in 14, consisted mainly of Grade I (WHO) nausea, drowsiness, cutaneous rash, and dizziness. Responders and patients with stable disease experienced a similar survival (median not reached at 22 months). Aminoglutethimide at low doses appears to be beneficial in patients refractory to conventional therapies even if the objective response rate is low.

The definition of the 'no change' category in patients treated with endocrine therapy and chemotherapy for advanced carcinoma of the breast

In the criteria used for assessment of response to treatment for advanced breast cancer the definition of no change (NC) is clear; however, there is no indication of the duration of stabilization required for patients to qualify for this category of response. We have made the assumption that NC is a worthwhile category of response if the overall time to progression (TTP) and survival of this group is not significantly different from patients with partial remissions (PR). Two hundred and sixty-three evaluable patients treated with endocrine therapy and 302 evaluable chemotherapy-treated patients were studied and the TTP and survival curves for PR and periods of NC from 1 to 6 months compared. For the endocrine-treated patients the TTP and survival curves for NC became non-significantly different from the PR curves after 4 and 5 months respectively. For chemotherapy-treated patients the TTP curves became non-significantly different from PR at 4 months and for survival the period was 3 months. In order to define NC as a useful category of response and to eliminate the possibility that NC taken for a shorter period could simply represent a slowly progressive tumour, we suggest that the minimum period of disease stabilization be taken as 5 months for both endocrine- and chemotherapy-treated patients.

Mechanisms of action of aminoglutethimide as endocrine therapy of breast cancer

During the last decade aminoglutethimide has been recognised as a valuable alternative in endocrine therapy for advanced breast cancer. Although some side effects do occur, most often these are initial effects which subside within a few weeks, and cessation of therapy is not usually indicated. Aminoglutethimide was originally introduced as an inhibitor of steroidogenesis in the adrenal cortex. It was soon recognised, however, that inhibition of the non-glandular aromatase, blocking the conversion of androgenic prohormones to oestrogens, was more important, resulting in decreased blood levels of oestrogens. In this review the role of aromatase inhibition as the only important aspect of the mechanism of action of aminoglutethimide is challenged. Evidence has accumulated during the last few years that aminoglutethimide is a most potent inducer of microsomal enzymes. In addition to the pharmacological implications this has (suggesting important interactions), it also points to the possibility that levels of oestrogens are decreased due to accelerated metabolism of these hormones. Based on new experimental data, and also clinical work with alternative aromatase inhibitors, it appears that the antitumour activity of aminoglutethimide may be due to both aromatase inhibition and accelerated metabolism of oestrogens. This seriously challenges the importance of aromatase inhibition alone as a strategy in endocrine therapy of breast cancer, and furthermore suggests that accelerated metabolism of key hormones is an alternative strategy to be explored.

Clinical pharmacology of aminoglutethimide in patients with metastatic breast cancer

The pharmacology of aminoglutethimide (AG) was studied in two subsequent trials without hydrocortisone supplementation. A total of 79 patients with metastatic breast cancer entered the study, and their plasma and urine samples were analyzed by high-performance liquid chromatography (HPLC). Thirty evaluable patients with a median age of 57 years (range, 37-79) were treated with the standard dose of 1000 mg/day, and 37 evaluable patients with a median age of 59 years (range, 35-79) received 500 mg/day. The median follow-up in the two groups was 5 months (range, 1-16) and 4 months (range, 1-21), respectively. After the first oral dose of 500 mg, peak plasma concentrations of AG were observed 1-4 h after administration in 15 patients. The elimination half-life was 10.1 +/- 1.7 h (mean +/- SD) after initial dosage; it decreased significantly to 6.9 +/- 1.2 h after 8 weeks of treatment. The area under the curve of AG concentrations was 92.5 +/- 14.2 micrograms/ml x h. The total clearance rate was 5.5 +/- 0.9 1/h and the volume of distribution was 80 +/- 111. About 23% of the drug was excreted unchanged in the urine. The major metabolite, N-acetyl-AG (AAG), had the same half-life as AG. A comparison on day 7 of treatment revealed that doses of 1000 and 500 mg yielded AG plasma concentrations of 9.0 +/- 1.2 and 4.5 +/- 0.5 micrograms/ml, respectively. After 1 month of treatment, however, AG plasma levels of 6-7 and 4-5 micrograms/ml were observed, respectively. A 50% reduction of dose, therefore, resulted in only 30% lower AG levels during continuous treatment. Apparently, the induction of metabolism is of greater importance in standard-dose than in lower dose treatment. The plasma concentrations of AG did not bear a relationship to the clinical response.

Variations in lipoproteins during aminoglutethimide therapy

Plasma lipids, apolipoproteins, and gamma-glutamyl-transpeptidase (GGT) were measured in 28 patients receiving aminoglutethimide (500 mg) and hydrocortisone (30 or 40 mg) for advanced breast cancer. A rise in cholesterol (CHOL), LDL-CHOL, apoprotein B, apoprotein CIII, and GGT was observed after 45 days. When the patients were divided in two groups according to lipid basal plasma levels, those with high CHOL and triglyceride did not experience any modification of lipid parameters (only GGT were elevated). Conversely normolipidaemic patients experienced an increase in CHOL, triglycerides, LDL-CHOL, apoproteins B and CIII, and GGT.

Endocrine effects of aminoglutethimide plus hydrocortisone versus effects of high dose of hydrocortisone alone in postmenopausal metastatic breast cancer

Aminoglutethimide (Ag) has been used in different dosages with and without combined treatment with glucocorticoids for the suppression of peripheral plasma levels of steroidal hormones. In the present work we have estimated changes in peripheral steroid levels after 3 days of adrenal suppression with a 'physiological' daily dose of 40 mg hydrocortisone (H). Subsequently Ag (1000 mg daily) was added or the dose of H was doubled in order to study the efficacy of the suppression of oestradiol by these conditions during a 6-week period. Sixteen postmenopausal patients with evaluable and measurable progressive breast cancer were selected for the initial treatment, thereafter Ag was added in eight patients, while the other eight patients continued on H with a double dose. Administration of 40 mg H daily during the first 3 days caused a significant decrease of plasma oestradiol (P less than 0.01), androstenedione (P less than 0.01) and DHEA-S (P less than 0.05). Basal plasma cortisol levels increased and the diurnal rhythm disappeared. These observations suggest suppression of adrenal function by the exogenous cortisol. Prolonged treatment with a higher dose of H (80 mg daily) caused further suppression of androstenedione (P less than 0.01) but not of oestradiol. The addition of 1000 mg of Ag to H had no further significant effect on plasma oestradiol levels either. The main difference between the effects of the two treatment modalities was in the levels of androgens. The group treated with H alone showed long-term significant suppression of both androstenedione and DHEA-S, while in the group treated with the combination of H + Ag a further pronounced suppression of DHEA-S and elevation of androstenedione was found. Finally, there was a significant difference between SHBG levels in the two groups at day 42. The increased levels of SHBG in the H + Ag-treated group might lower the 'free' oestradiol concentration. It is concluded that both drugs have different effects on the plasma levels of peripheral steroids. On theoretical grounds, the combination of H + Ag might be preferable, because 'free' oestradiol plasma levels may be lowest after this treatment. However, a direct correlation with clinical effects still remains to be proven.