Duffy S, Jackson TL, Lansdown M, Philips K, Wells M, Pollard S, Clack G, Coibion M, Bianco AR. The ATAC (‘Arimidex’, Tamoxifen, Alone or in Combination) adjuvant breast cancer trial: first results of the endometrial sub-protocol following 2 years of treatment.
Hum Reprod 2005;
21:545-53. [PMID:
16210385 DOI:
10.1093/humrep/dei322]
[Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND
Tamoxifen treatment results in a doubling of the risk of endometrial cancer after 1-2 years of treatment and a quadrupling after 5 years. Anastrozole, a third-generation aromatase inhibitor, with superior efficacy to tamoxifen, may also offer tolerability benefits in terms of effects on the endometrium.
METHODS AND RESULTS
A sub-protocol of the ATAC trial compared the incidence/type of intrauterine changes following treatment with these agents in a subgroup of patients (n = 285) from the main trial. After 2 years anastrozole treatment, endometrial thickness remained </= 5 mm (baseline: 3.0 mm); in patients receiving tamoxifen, endometrial thickness increased by 3.2 mm to 7.0 mm, with a similar trend in the combination group. At baseline, 26/285 patients (9.1%) had endometrial abnormalities, most commonly polyps. After 2 years the number of endometrial abnormalities appeared lower with anastrozole treatment compared with tamoxifen although these differences were not statistically significant (odds ratio: 0.44; 95% confidence interval 0.146, 1.314; P = 0.14). Most abnormalities occurred within the first year of treatment (anastrozole: 4/6; tamoxifen: 7/10; combination: 10/16; total: 21/32). Fewer patients in the anastrozole group (1.4%) required medical intervention (tamoxifen 12.5%; combination 13.6%).
CONCLUSIONS
Fewer endometrial abnormalities occurred during 2 years treatment with anastrozole compared with tamoxifen although statistical significance was not reached in this sub-protocol analysis.
Collapse