Second line hormonal therapy with aminoglutethimide in metastatic breast cancer

Aromatase inhibitors: past, present and future in breast cancer therapy

Estrogen has been implicated in promoting breast cancer in a majority of women. Endocrine therapy controlling estrogen production has been the guiding principle in treating breast cancer for more than a century. A greater understanding of this disease at a molecular level has led to the development of molecules that inhibit estrogen production by inhibiting the aromatase enzyme, that is the primary source of estrogen in postmenopausal women. This review examines the evolution of aromatase inhibitor (AI) based therapies over the past three decades. The third generation aromatase inhibitors (anastrozole, letrozole and exemestane), which have been found to be extremely specific and effective in an adjuvant/neoadjuvant/extended adjuvant setting are discussed from a biochemical and clinical perspective. A comprehensive discussion of the past, present, and future of aromatase inhibitors is conducted in this review.

Neoadjuvant endocrine therapy in breast cancer

The use of endocrine therapy is well established as a primary treatment for locally advanced breast cancer. However, despite the current popularity of neoadjuvant chemotherapy for operable tumours, there is relatively little published evidence for pre-operative endocrine therapy in operable disease, particularly outside of the elderly population. The wider use of aromatase inhibitors (AIs) has encouraged studies that compare the efficacy of AIs with tamoxifen in the neoadjuvant setting, but there remains a lack of comparison of neoadjuvant with adjuvant endocrine therapies. This review discusses the current evidence regarding primary endocrine therapy, along with the factors involved in choosing appropriate patients for neoadjuvant therapy and the current opinions on length of treatment time and measurement of response prior to surgery.

Endocrine therapy in metastatic breast cancer

Endocrine therapy represents a mainstay of effective, minimally toxic, palliative treatment for metastatic breast cancer. Research focusing on the mechanism of action of endocrine agents will provide new insights leading to new hormonal approaches in breast cancer treatment. Development of new agents, especially the 'pure' antiestrogens, is of great interest. Combining endocrine therapy with biologic agents, especially antiproliferative compounds, may lead to more effective treatment in the adjuvant as well as the advanced setting. Tables 4 and 5 summarize response rates to the different groups of endocrine agents used in metastatic breast cancer and doses of commonly used agents, respectively. At present, tamoxifen is the drug of choice as first-line endocrine therapy for metastatic breast cancer with no or minimal symptoms in premenopausal or postmenopausal women. Second-line therapy usually consists of megace. Aromatase inhibitors may be used as second- or third-line therapy in postmenopausal women. In premenopausal women, LHRH analogues are a reasonable choice. The other hormonal agents may be beneficial as salvage therapy. More effective endocrine approaches are under development.

Hormonal treatment for metastatic breast cancer. An Eastern Cooperative Oncology Group Phase III trial comparing aminoglutethimide to tamoxifen

BACKGROUND

Tamoxifen and aminoglutethimide are two hormone therapies reported to be effective palliative approaches for patients with metastatic breast cancer. The current trial was designed to evaluate their relative therapeutic effectiveness.

METHODS

Two hundred forty-nine postmenopausal women with advanced breast cancer were randomized in an Eastern Cooperative Oncology Group (ECOG) Phase III study to treatment with adrenalectomy, aminoglutethimide, or tamoxifen with crossover to alternate therapy if disease progressed. Adrenalectomy was dropped as a treatment after 2 years because of low patient accrual.

RESULTS

There were 216 evaluable patients entered in the study with 108 initially randomized to aminoglutethimide and 108 to receive tamoxifen therapy. The overall response rate for aminoglutethimide was 45%, and for tamoxifen it was 27%. One institution had a response rate of 60% with aminoglutethimide and only 4% with tamoxifen, whereas all of the other institutions combined had a response rate of 41% with aminoglutethimide and 34% with tamoxifen. Eighty-seven evaluable patients crossed over to the other drug (44 to aminoglutethimide and 43 to tamoxifen). There was a 36% response rate to aminoglutethimide and 19% to tamoxifen, with stable disease in 36% of both groups. The overall survival rates were identical. Toxicity was greater with aminoglutethimide (dermatitis) but was not life-threatening. Glucocorticoid support with either dexamethasone or hydrocortisone was acceptable.

CONCLUSIONS

Both aminoglutethimide and tamoxifen produced responses in postmenopausal patients with breast cancer, and a significant number of crossover responses were observed. Of interest in this randomized study was the observation that one institution had a markedly different response rate on induction, reinforcing the need for multi-institution trials in Phase III studies.

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.