Update of the Royal Marsden Hospital tamoxifen breast cancer chemoprevention trial
T. J. Powles, R. Eeles, A. Salmon, A. Tidy, S. Ashley, M. Dowsett;
The Royal Marsden Hospital/Institute of Cancer Research, London, UK; Royal Marsden Hospital, London, UK
This trial randomised 2471 healthy women aged 30-70 with a family history of breast cancer to tamoxifen 20 mgs/day or placebo for up to 8 years.
We previously reported, after a median follow up of 70 months, that a total of 70 breast cancers had occurred with no evidence of a risk reduction by tamoxifen(1).
We now have a median follow up of 123 months and there is still no evidence of a significant risk reduction of breast cancer by tamoxifen in this trial (tamoxifen 69, placebo 82, p=0.3) although there was a trend for risk reduction (HR 21%, p=0.12) for women on HRT who took tamoxifen.
Breast cancers developing on tamoxifen are more likely to be oestrogen receptor negative (22/66; 35%) than those developing on placebo (14/75; 19%) (p=0.03) especially in postmenopausal women (tamoxifen 9/20; 45%, placebo 2/20; 9%) (p=0.01).
An analysis using the Claus model for genetic risk did not identify a subgroup of women who gained a significant benefit from tamoxifen. We are now evaluating other risk factors as possible markers of possible benefit.
Reference: 1. Powles T, Eeles R, Ashley S, et al: Interim analysis of the incidence of breast cancer in the Royal Marsden Hospital tamoxifen randomised chemoprevention trial. Lancet 352:98-101, 1998
Category: Late-Stage Clinical Trials
ASCO Abstract No: 375, 2003
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