Therapeutic use of tamoxifen in advanced breast cancer: correlation with biochemical parameters

Abstract

Tamoxifen (NSC-180973; ICI-46474) can provide palliation to patients with advanced breast cancer whose tumors contain estrogen-binding proteins (EBP). The drug is most effective in patients with bone metastasis and minimal prior therapy. In the present study, 72 patients with advanced breast cancer were evaluated for their response to oral tamoxifen therapy administered at a dose of 20 mg twice daily. Twenty-eight of 72 patients (38%) demonstrated objective responses to tamoxifen therapy. For patients with a positive EBP and no prior chemotherapy, eight of 11 (74%) responded. No patient possessing a tumor negative for EBP achieved a remission. Patients with tumors that possessed normal arylsulfatase B and glucose-6-phosphate dehydrogenase enzyme activities responded most favorably to tamoxifen therapy. These results demonstrate that tamoxifen is effective in the treatment of patients with advanced breast cancer, and EBP and specific enzymes might be useful in selecting the patients for hormone manipulation.

PIP: Tamoxifen is a synthetic nonsteroidal drug with antiestrogenic properties. This report describes the response of patients with metastatic breast cancer to tamoxifen and correlates clinical responses with tumor tissue content of cytoplasmic estrogen binding proteins (EBPs) and other biochemical parameters. Ages of patients ranged from 27 to 82 years. 7 patients were premenopausal, 63 postmenopausal, and 2 had recent endocrine ablaetion. Prior hormone therapy, radiotherapy, or chemotherapy ahd been given to all patients. Tamoxifen was given at a dose of 20 mg orally for a minimum of 4 weeks and continued if an objective remission was shown. Before therapy a biopsy specimen was taken for determination of EBP and for specific enzyme activities. Another biopsy specimen was taken for at least 8 weeks after therapy. A total of 72 patients were treated for at least 4 weeks. The overall response rate was 38%. Most frequent responses were in the over-70 age group. The median duration of response has been 9.5 months. Bony involvement responded to therapy in 21 of 28 patients. No responses were shown in 6 patients with liver metastases. Only 1 of 18 patients who had previous chemotherapy responded. Of 31 who had no prior chemotherapy, 73% achieved a remission. There was a 44% correlation between patients with a positive EBP assay and response to therapy, but none in EBP-negative patients. In this study 20 of 28 patients had normal arylsulfatase B/DNA ratios in their tumor tissue and 11 of the 20 responded to tamoxifen therapy. Patients who responded most favorably to therapy had normal G-6-PD activities. It is concluded that tamoxifen therapy may cancel the need for ablative surgery in postmenopausal patients with positive EBPs and who have had a prior response to additive hormonal treatment.