Low Breast Cancer Rates with Tamoxifen
Cancer is a great tragedy today. Recently, some studies were hold in a way for the Ibis. We will tell you about the results of the study.
As for the Ibis, one study began in 1992 and is very mature now in the sense that we have more than 20 years of follow-up in some patients 16 years median follow-up. It was a trial of Tamoxifen for five years at the standard 20-milligram dose or matching placebo. High-risk patients without breast cancer entered into this trial.
There were women, who were volunteers. They were high-risk, and they agreed to take Tamoxifen. These were women, who had a family history of breast cancer, and we're very concerned about not on their risk, but the risk of their daughters and family as well and offered to join the trial to help us learn how best to prevent breast cancer.
We got sixteen years of follow-up that is quite a long time. We knew from previous analyses that after about ten years that Tamoxifen was preventing a lot of cancers, about a third of the cancers were, actually, being prevented not only in the five years of active treatment, but there was a five-year carryover. In the next five years, we saw a similar-sized benefit. What is new is that we now have good evidence from 10 to 20 years overall. We found that the benefits have continued for another 10 years. In the next 10 years, we also prevented another 30% of the breast cancers that would have occurred in the placebo population.
There is a downside to using tamoxifen for five years, all of these drugs. That is because they reduced estrogen levels produce estrogen like withdrawal symptoms, like the menopause. Some women have hot flushes, night sweats, all that standard menopausal problems. The specific side effect of Tamoxifen is an increase in endometrial cancer, which we saw previously. We reported it in our eight-year follow-up. What is new this time is that we have seen some of those cancers that have been fatal, which, we hope, was not going to be the case. However, in fact, we now have five deaths in the Tamoxifen. They are from endometrial cancer and none in the control.
As for hormone replacement therapy, then this was a study in women without breast cancer. There is no knowing what kind of cancer they would develop. One of the decisions that we argued about was whether we would allow women to take concurrent hormone replacement therapy. We decided that this was acceptable, as did the other European trials, the American P1 trial decided not to allow this. In retrospect now, we have seen that, in fact, the effects of Tamoxifen are very weak, when women are also taking hormone replacement therapy, and they are much stronger if they did not take hormone replacement therapy at the time they were taking Tamoxifen. There are the benefits in women, who did not take hormone replacement therapy instead of 30% there are 38%, which is a substantial increase.
Benefits of Tamoxifen Therapy
We have shown very clearly now that five years of Tamoxifen has a very long lasting effect on reducing breast cancer. By about 30% overall a bigger effect was seen in women, who did not take hormone replacement therapy, where it was almost 40%. The trial is still too immature to look at mortality, less than 5% of the women on the trial have died. It is going to take us another five to ten years to understand if these benefits will translate into a mortality reduction, which we have not seen at this stage.
Women should try it if they think that they have an increased risk of breast cancer. It is always worthwhile trying it. If the symptoms are really very difficult or intolerable, then there's no just simply stop. Most of the affected the symptoms in terms of menopausal symptoms will disappear within a few months. It may be a reason not to continue.
The data are quite clear that Tamoxifen does prevent breast cancer, but there are some side effects. The reduction is about 30%. Last year we showed that the use of enrollment ACE inhibitor would reduce breast cancer incidence by about 50%, probably, with fewer side effects. Nevertheless, that is only for postmenopausal women.
Therefore, these results are, probably, particularly important for high-risk premenopausal women, of course, because they are younger and have longer to live. This long-term benefit is very important for them. We estimate that you only need to treat 22 women to prevent one breast cancer. It may be even better than that for younger premenopausal women.
The brief take-home message is that Tamoxifen is a very attractive option for high-risk premenopausal women and they should consider it seriously.