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Gynaecological Tolerability Advantage of Anastrozole Confirmed: Presented at SGOC

By Joanna Lyford

ST. GALLEN, SWITZERAND -- March 19, 2007 -- The superior tolerability of anastrozole over tamoxifen in women with early breast cancer is likely to translate into benefits to their psychological well being, quality of life, and economic well being, researchers report.

Their conclusion is based on a new analysis of the Arimidex, Tamoxifen, Alone or in Combination (ATAC) study, a large randomised trial comparing the aromatase inhibitor anastrozole with tamoxifen in 9,366 postmenopausal women with early breast cancer.

Anastrozole is a nonsteroidal third-generation aromatase inhibitor that is devoid of oestrogenic activity and is therefore anticipated to cause fewer gynaecological effects than tamoxifen. This hypothesis was tested in a substudy of ATAC and the results presented in a poster session here on March 15^th at the 10^th International St. Gallen Oncology Conference: Primary Therapy of Early Breast Cancer (SGOC), held in St. Gallen, Switzerland.

Wolfgang Distler, MD, director, gynaecology and obstetrics, Carl Gustav Carus University Clinic, Dresden, Germany, analysed data from the endometrial substudy that included 97 women on anastrozole and 89 on tamoxifen. All women had an intact uterus at baseline. They were assessed at regular intervals during follow-up for endometrial abnormalities and thickness using transvaginal ultrasonography, hysteroscopy, and pipelle sampling.

After 5 years of follow-up, anastrozole was associated with a significantly lower incidence of gynaecological adverse events versus tamoxifen. Four symptom categories were markedly less common with anastrozole: vaginal haemorrhage (5.2% vs 8.3%), leucorrhoea (2.7% vs 9.7%), endometrial hyperplasia (0.7% vs 6.1%), and endometrial neoplasia (1.0% vs 5.3%).

Endometrial abnormalities typically arose during the first year of treatment, the study authors comment, and most were due to polyp formation. Endometrial thickness was unchanged during follow up in the anastrozole group but increased by 2 mm, on average, in those receiving tamoxifen.

Furthermore, anastrozole-treated women were less likely than their tamoxifen-treated counterparts to undergo either diagnostic (21.8% vs 29.4%) or therapeutic (8.5% vs 15.4%) interventions. They were also significantly less likely to need a hysterectomy for either malignant or benign disease (1.3% vs 5.1%).

The lower rate of gynaecological and endometrial adverse events is likely to save women "additional physical suffering and psychological distress," according to the investigators. "It will also reduce the economic burden to the healthcare provider."

They conclude: "Since the excess adverse events with tamoxifen occur early in treatment, the data also indicate that commencing adjuvant treatment with anastrozole is more beneficial than a sequence of 2 to 3 years' tamoxifen followed by an aromatase inhibitor."


[Presentation title: Fewer Gynaecological Adverse Events (AES), Gynaecological Interventions, Endometrial Changes and Abnormalities With Anastrozole Than With Tamoxifen: Findings From the ATAC (`Arimidex', Tamoxifen, Alone or in Combination) Trial. Abstract P115]

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