Efficacy and tolerability of 4-hydroxyandrostenedione (4-OHA) as first-line treatment in postmenopausal patients with breast cancer after adjuvant therapy

Aromatase inhibitors: the journey from the state of the art to clinical open questions

Breast cancer is a major cause of death among females. Great advances have been made in treating this disease, and aromatase inhibitors (AIs) have been recognized as the cornerstone. They are characterized by high efficacy and low toxicity. The authors reviewed the available literature and defined state-of-the-art AI management. This study was designed to assist clinicians in addressing the need to equally weigh patients' needs and disease control rates in their everyday clinical practice. Today, AIs play a central role in the treatment of hormone receptor-positive breast cancer. In this study, an expert panel reviewed the literature on the use of AIs, discussing the evolution of their use in various aspects of breast cancer, from pre- and postmenopausal early breast cancer to metastatic breast cancer, along with their management regarding efficacy and toxicity. Given the brilliant results that have been achieved in improving survival in everyday clinical practice, clinicians need to address their concerns about therapy duration and the adverse effects they exert on bone health, the cardiovascular system, and metabolism. Currently, in addition to cancer treatment, patient engagement is crucial for improving adherence to therapy and supporting patients' quality of life, especially in a selected subset of patients, such as those receiving an extended adjuvant or combination with targeted therapies. A description of modern technologies that contribute to this important goal is provided.

Meta-analyses of phase 3 randomised controlled trials of third generation aromatase inhibitors versus tamoxifen as first-line endocrine therapy in postmenopausal women with hormone receptor-positive advanced breast cancer

BACKGROUND

Four randomised controlled trials (RCTs) in postmenopausal women with advanced breast cancer (ABC) comparing aromatase inhibitors (AIs) versus the selective estrogen receptor modulator tamoxifen, each individually reported significantly longer progression-free survival (PFS) but none showed a significant difference in overall survival (OS). In these trials between 6.8% and 55% of tumours were hormone receptor (HR) status unknown or negative. This meta-analysis restricted the comparison to HR-positive (HR+) tumours.

METHODS

Anonymised individual patient data were obtained from three RCTs, EORTC (exemestane versus tamoxifen), Study 0027 and Study 0030 (both anastrozole versus tamoxifen). For the remaining RCT (Femara Study PO25; letrozole versus tamoxifen), odds ratio (OR) or hazard ratio (HzR), with confidence intervals were obtained from the clinical study report, for patients with HR+ tumours, in addition to published data. In total, data were obtained from 2296 patients; 1560 (68%) had HR+ ABC.

FINDINGS

The OR for clinical benefit rate was 1.56, in favour of AIs (p < 0.001). The duration of clinical benefit was not significantly increased by AIs (HzR 0·88; p = 0.08). For PFS the HzR (0.82) was in favour of AIs (p = 0·007). However, for OS the HzR (1.05) was not significantly different between AIs and tamoxifen (p = 0.42).

INTERPRETATION

Although third generation AIs put significantly more patients into 'clinical benefit', their tumours were not controlled for significantly longer. Overall, while this resulted in a significantly greater PFS in favour of the AIs, this did not translate into improvement in OS.

Formestane as Treatment of Advanced Breast Cancer in Elderly Women

Aims and background

The number of elderly people is increasing, and the proportion of breast cancer in female cancer patients older than 65 years is 26%. In elderly patients, hormone therapy is widely accepted as the treatment of choice, because of its efficacy and good tolerability compared to chemotherapy. The aim of this study was to evaluate the endocrinologic and clinical activity of formestane (4-hydroxyandrostenedione), a selective aromatase inhibitor, in elderly patients with advanced breast cancer.

Methods

Thirty-five patients older than 65 years, selected from a larger group, were given formestane (250 mg or 500 mg i.m. fortnightly). Patients were evaluable for tumor response after 4 doses of formestane. Blood samples were collected to evaluate E2, FSH, LH, SHBG and DHEAS serum levels at baseline and after 2, 4, 8,12 and 24 weeks.

Results

Thirty patients had PS ≤ 1 (ECOG) and only 5 patients had PS = 2. Twenty-six patients were ER positive. Previous hormonal treatment for metastatic disease had been given to 17 patients; only 1 case had received chemotherapy. The overall response rate was 51% (95% C.I. 35–67%) and the median response duration was 9.5 months. Three complete responses were observed on viscera. The best responses were obtained on soft tissues (59%); on bone and viscera the response was respectively 45% and 47%. Local and systemic tolerability was highly satisfactory. Formestane induced prolonged suppression of E2 levels in all of the patients, and a significant reduction in SHBG levels was also observed from month 2 onward. A statistically significant ( P = 0.0001) rise in serum FSH was also observed during the therapy.

Conclusions

The study showed that formestane induced a long-lasting suppression of E2 levels and a satisfactory overall response. In our opinion, the drug is an effective and well-tolerated approach in the management of advanced breast cancer in elderly patients.

The effects of aromatase inhibitors and antiestrogens in the nude mouse model

The effects of antiestrogens, tamoxifen and ICI 182,780, and aromatase inhibitors, arimidex (anastrozole ZD1033) and letrozole (CGS 20,267), on the growth of tumors were studied in nude mice. In this model, estrogen dependent MCF-7 human breast cancer cells stably transfected with the aromatase gene were inoculated in four sites per mouse. Sufficient estrogen is produced from aromatization of androstenedione supplement (0.1 mg/mouse/day) by the cells to stimulate their proliferation, tumor formation, and maintain the uterus similar to that of the intact mouse. Once the tumors reached a measurable size, the mice were injected with antiestrogen or inhibitor for 35-56 days. Tumor volumes were measured weekly. At autopsy, the tumors were removed, cleaned, and weighed. Statistical data was determined from tumor weights. Both antiestrogens were effective in reducing tumor growth in these mice. Tamoxifen appears to be more effective than ICI 182,780, although the former stimulated the uterine weight whereas the pure antiestrogen did not. However, both aromatase inhibitors were more effective than the antiestrogens. Tumor regression was observed with letrozole. Thus, after-treatment tumor weights were less than those of a group of mice at the start of treatment. The aromatase inhibitors also reduced the weight of the uterus, suggesting that these compounds, as well as the pure antiestrogen, may not cause endometrial proliferation, unlike tamoxifen. These aromatase inhibitors may not only benefit patients who have relapsed from tamoxifen, but may be more effective in patients as first line agents for suppressing the effects of estrogen.

Mechanisms of action of endocrine treatment in breast cancer

Endocrine treatment plays an important role in the therapy of breast cancer. While the basic mechanisms are understood, additional mechanisms may be of importance to their action and they may also contribute to the mechanism(s) of acquired resistance. Currently, several novel drugs are entering into clinical trials. Observations of the absence or presence of cross resistance to novel 'pure' steroidal antiestrogens and the non-steroidal tamoxifen may add important information to our understanding of the mechanisms of action of both classes of drugs. Similarly, exploration of different aromatase inhibitors in sequence or concert, as well as the combining of different endocrine treatment options may be warranted. Additionally, alterations in different biochemical parameters such as growth factors should not only be carefully explored in relation to treatment options but should also be followed during the course of treatment to asess alterations over time and in relation to the development of drug resistance.

Endocrinological and clinical evaluation of exemestane, a new steroidal aromatase inhibitor

The androstenedione derivative, exemestane (FCE 24304), is a new orally active irreversible aromatase inhibitor. Fifty-six post-menopausal advanced breast cancer patients entered this study to evaluate the activity of four low exemestane doses in reducing oestrogen levels. The drug's tolerability and clinical efficacy were also assessed. Exemestane was orally administered to four consecutive groups at daily doses of 25, 12.5, 5 and 2.5 mg, and the changes in oestrogen, gonadotrophins, sex-hormone binding globulin and dehydroepiandrosterone sulphate levels were evaluated. Drug selectivity was studied by measuring 17-hydroxycorticosteroid urinary levels. After 7 days of treatment, mean oestrone and oestradiol levels had decreased by respectively 64% and 65% (a decrease which was maintained over time); in the 2.5 mg group, oestrone sulphate levels also decreased by 74%. Gonadotrophin levels were significantly higher, whereas no changes in the other serum hormone levels or any interference with adrenal synthesis were detected. Treatment tolerability was satisfactory: nausea and dyspepsia were reported in 16% of patients. The overall objective response rate was 18%. In conclusion, exemestane is effective in reducing oestrogen levels at all of the tested doses and shows interesting clinical activity.

Formestane: an effective first-line endocrine treatment for advanced breast cancer

Formestane, a new selective aromatase inhibitor devoid of severe side-effects, has been shown to be active in patients with advanced breast cancer. To investigate the clinical activity and endocrinological effects of formestane as a first-line treatment, 52 patients were administered two different doses: 24 received 250 mg formestane and 28 received 500 mg formestane i.m. fortnightly. All of the patients had a performance status of 2 or less (ECOG scale), 34 (65%) had a disease-free interval of at least 2 years and 21 (40%) were both oestrogen-receptor- and progesterone-receptor-positive; 20 patients received hormone and 13, received chemotherapeutical adjuvant treatment. Objective responses were obtained in 8 patients in the 250-mg group (33%; 95% CI: 14%-52%) and in 13 patients in the 500-mg group (46%; 95% CI: 28%-64%). The median response duration in the two groups was respectively 11 and 12 months. E2 serum levels of oestradiol had significantly (P < 0.001) decreased to more than 40% below the baseline value in both groups after 15 days of treatment, and remained unchanged thereafter. Local and systemic tolerability was satisfactory. We conclude that formestane is an effective and well-tolerated agent in previously untreated patients, and that these results should be confirmed by further studies.

The effects of oral 4-hydroxyandrostenedione on peripheral aromatisation in post-menopausal breast cancer patients

This study investigated the influence of the aromatase inhibitor 4-hydroxyandrostenedione (4OHA, formestane), given orally, on peripheral aromatase activity and plasma oestradiol (E2) levels in post-menopausal women with advanced breast cancer. The aim was to establish whether an optimal dose could be identified that had a pharmacological effectiveness comparable with that of parenteral 4OHA. A total of 13 post-menopausal women were studied before treatment and after a minimum of 4 weeks on treatment with one or more of the following doses: 125 mg once daily (od), 125 mg b.i.d. (bd) and 250 mg od. In all, seven aromatase studied were performed at 125 mg od; four, at 125 mg bd; and ten, at 250 mg od. Three patients were studied at all doses. E2 was measured concurrently and was available at all dose increments for seven patients. Given at doses of 125 mg od, 125 mg bd and 250 mg od, treatment with formestane inhibited in vivo aromatisation by 62.3% +/- 9.5%, 70.0% +/- 5.1% and 57.3% +/- 5.3%, respectively (mean +/- SEM). Corresponding values for plasma E2 suppression were 30.7% +/- 6.5%, 43.4% +/- 4.5% and 42.9% +/- 6.7%, respectively. Thus, apart from a somewhat better suppression of plasma E2 levels by the two higher doses as compared with 125 mg od, no significant difference in the degree of aromatase inhibition or plasma E2 suppression was observed. The suppression of E2 by oral 4OHA at 125 mg bd or 250 mg od approaches that achieved by the recommended parenteral schedule of 250 mg fortnightly, but inhibition of aromatase at this dose was substantially inferior. The findings are consistent with a hypothesis that 4OHA given orally may cause substantial plasma oestrogen suppression during part of the day, but neither the od nor the bd regimens investigated in the present study were capable of producing optimal aromatase inhibition.

Endocrinological and clinical evaluation of two doses of formestane in advanced breast cancer

Formestane is a selective inhibitor of oestrogen synthesis by aromatase enzymes and induces disease regression in breast cancer patients. This phase II randomised study was carried out to determine whether there were any differences in the effects of two different doses of formestane on oestradiol (E2) serum levels and to evaluate the corresponding clinical activity in post-menopausal patients with positive or unknown oestrogen receptor status pretreated or not for advanced disease. Furthermore, possible drug interference with adrenal steroidogenesis was assessed by measuring 17-hydroxycorticosteroid (17-OHCS) urinary levels. A total of 143 patients entered the study and were randomly assigned to receive formestane 250 mg (72 patients) or formestane 500 mg (71 patients), both given i.m. every 2 weeks. In comparison with baseline, E2 serum levels decreased by an average of 40% after only 15 days and remained unchanged thereafter, with no difference being observed between the two doses. The values of 17-OHCS remained unchanged during treatment in both groups. Objective responses were 28% (19/69) in the 250 mg and 46% (31/68) in the 500 mg group. In conclusion, the two formestane doses were equally effective in reducing E2 levels without affecting adrenal function, and in inducing a considerable percentage of clinical responses.