Droloxifene, a new antiestrogen. Hormonal influences in postmenopausal breast cancer patients

The evolving role of specific estrogen receptor modulators (SERMs)

Estrogens are the most effective therapy for women with postmenopausal problems. However, relatively few women use estrogen and then often for a limited time because of the fear of its carcinogenic effects on the uterus and breast; in addition, estrogen is not advised for women who have had breast cancer. Selective estrogen receptor modulators (SERMs) are agents with antagonist action on the uterus and breast and agonist action on the bones, cardiovascular system, and brain. Unlike estrogens, however, existing SERMs do not help alleviate the vasomotor and urogenital problems associated with menopause. A comprehensive review of the literature published from January 1995 to June 1999 was conducted. Reports were identified using Medline and Cancer Lit. The effect of menopausal problems on the health of women and the socioeconomic effects of menopause are discussed. All currently available and investigational SERMs are reviewed and discussed, including their mechanism of action, metabolism, dose scheduling, antitumor activity, and potential role in maintaining the health of menopausal women and in preventing breast cancer.

Steroid Hormone Levels in Patients with Advanced Breast Cancer during Therapy with Droloxifene: A Pilot Study

Antiestrogens, particularly tamoxifen, are effective in the treatment of pre- and postmenopausal women suffering from all stages of breast cancer. Unfortunately, many patients become resistant to tamoxifen during therapy, which allows the tumor to progress. Thus, a preclinical recognition of tumor progression, i.e. by monitoring serum hormone levels, could be worthwhile. The serum levels of dehydroepiandrosterone sulfate and estradiol of postmenopausal women with advanced breast cancer treated by the new antiestrogen droloxifene were therefore checked. However, only non-significant changes in the hormone levels during droloxifene therapy were observed, and no relation was found between hormone levels and the course of the disease, success or exhaustion of droloxifene application, or development of tumor progression. Our data do not confirm earlier findings reported in the literature that measurement of hormones seems to be suitable for an early indication of tumor progression during an antiestrogen therapy before its clinical manifestation.

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.

Droloxifene, a new anti-oestrogen in postmenopausal advanced breast cancer: preliminary results of a double-blind dose-finding phase II trial

Droloxifene (3-OH-tamoxifen citrate) is a novel anti-oestrogen with a higher affinity for oestrogen receptors (ER), a lower oestrogenic to anti-oestrogenic activity ratio and faster pharmacokinetics compared with tamoxifen. From May 1988 to April 1991, 369 postmenopausal women with metastatic or locally unresectable breast cancer of which the ER or progesterone receptor status was positive or unknown, were randomised to receive an oral dose of 20, 40 or 100 mg droloxifene once daily. 43 Brazilian, Canadian and European centres took part in this double-blind phase II trial. 60 women were ineligible for violation of entry criteria; 20 were inevaluable and 15 still await definitive response evaluation. 234 patients have been evaluated for response. The over-all objective response rate (complete plus partial) was 92/234 (39.3%): 23/74 (31.1%) for 20 mg, 33/74 (44.6%) for 40 mg and 36/86 (41.9%) for 100 mg (not significantly different within this dose range). There was no significant difference in time to tumour progression between the three doses. Toxicity was minimal at all doses. These preliminary results show that droloxifene is active against advanced breast cancer. Because of its outstanding preclinical characteristics, the drug warrants large-scale clinical investigation.