Combined treatment with buserelin and tamoxifen in premenopausal metastatic breast cancer: a randomized study.
BACKGROUND
Surgical or medical castration and antiestrogenic treatment with tamoxifen are common endocrine treatments for premenopausal women with breast cancer. However, tamoxifen therapy induces high levels of plasma estradiol, with unknown long-term effects. In this study, we investigated the effect of combining estrogen suppression with the luteinizing hormone-releasing hormone agonist buserelin and estradiol receptor blockade with tamoxifen to determine whether the high estradiol levels induced by tamoxifen could be reduced and whether the antitumor effects would be better.


METHODS
In a three-arm, randomized, prospective trial, from 1988 through 1995, a total of 161 premenopausal patients with advanced breast cancer were randomly assigned to treatment with buserelin, tamoxifen, or both. Patients with steroid receptor-negative tumors or with tumors of unknown receptor status who had a disease-free interval of less than 2 years were excluded. The median follow-up was 7.3 years, during which 76% of the patients died, all of breast cancer. Patient and tumor characteristics were well balanced among treatment groups. All P values are from two-sided tests.


RESULTS
Combined treatment with buserelin and tamoxifen was superior to treatment with buserelin or tamoxifen alone by objective response rate (48%, 34%, and 28% of patients who could be evaluated, respectively; P =.11 [chi(2) test]), median progression-free survival (9.7 months, 6.3 months, and 5.6 months; P =.03), and overall survival (3.7 years, 2.5 years, and 2.9 years; P =.01). Actuarial 5-year survival percentages were 34.2% (95% confidence interval [CI] = 20.4%-48.0%), 14.9% (95% CI = 3.9%-25.9%), and 18.4% (95% CI = 7.0%-29.8%), respectively. No differences in antitumor effects were observed between single-agent treatment groups. During combined treatment or treatment with buserelin alone, plasma estradiol levels were suppressed equally; in contrast, during treatment with tamoxifen alone, plasma estradiol levels increased threefold to fourfold over pretreatment levels.


CONCLUSIONS
Combined treatment with buserelin and tamoxifen was more effective and resulted in longer overall survival than treatment with either drug alone.
Klijn
J G
JG
Department of Medical Oncology, Rotterdam Cancer Institute, University Hospital Rotterdam, The Netherlands. bos@onch.axr.nl
Beex
L V
LV
Mauriac
L
L
van Zijl
J A
JA
Veyret
C
C
Wildiers
J
J
Jassem
J
J
Piccart
M
M
Burghouts
J
J
Becquart
D
D
Seynaeve
C
C
Mignolet
F
F
Duchateau
L
L
D000328:Adult; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000097:blood / Q000188:drug therapy*; D002064:Buserelin / Q000627:therapeutic use*; D018572:Disease-Free Survival; D004359:Drug Therapy, Combination; D004958:Estradiol / Q000097:blood; D020847:Estrogen Receptor Modulators / Q000627:therapeutic use*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood; D006801:Humans; D008597:Menstrual Cycle / Q000187:drug effects; D008875:Middle Aged; D017697:Premenopause; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D020845:Selective Estrogen Receptor Modulators / Q000627:therapeutic use*; D016019:Survival Analysis; D013629:Tamoxifen / Q000627:therapeutic use*; D013997:Time Factors; D016896:Treatment Outcome
D018931:Antineoplastic Agents, Hormonal; D020847:Estrogen Receptor Modulators; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D002064:Buserelin