Which women decide to take tamoxifen?

To identify factors which predict, among estrogen receptor (ER)-positive breast cancer patients, who chooses to take adjuvant tamoxifen.

We studied 1347 women with ER-positive breast cancer who were treated at Women's College Hospital between 1987 and 2000. For each patient, we obtained information on age at diagnosis, tumour size, lymph node status, ER status, treatments received and dates of local recurrence and of death. We compared women who did and who did not take tamoxifen for a range of factors. We used the Kaplan-Meier method to estimate 15-year local recurrence-free and breast cancer-specific survival rates for women who did and who did not take tamoxifen.

Overall, 50.4% of women who had a mastectomy took tamoxifen and 61.0% of women who had a lumpectomy took tamoxifen (p = 0.002). Tamoxifen use did not correlate with any of the factors that were predictive of a high risk of death from breast cancer, such as young age, large tumour size and positive lymph node status. Young women (<40 years) experienced much higher mortality (41.1%) than older (>60 years) women (14.1%, p < 0.01), but were much less likely to have taken tamoxifen (35.0 vs. 74.6%, p < 0.01).

Approximately one-half of women with ER-positive breast cancer who are candidates for tamoxifen did not take tamoxifen. Women with lumpectomy were more likely to take tamoxifen than women with mastectomy. Paradoxically, women at high risk of death from breast cancer (less than 40 at diagnosis and/or lymph node positive) and who are expected to receive the greatest benefit from tamoxifen in terms of mortality reduction were less likely to take it than were low-risk women (older women, lymph node negative). These findings suggest that women consider the reduction in risk from local recurrence to be more important than the reduction in risk of death from breast cancer when they consider taking tamoxifen.