Starting tamoxifen early and continuing it for around five years halved the recurrence rate, irrespective of age, and improved long-term survival. It was effective whether or not chemotherapy had been given, and whether or not the cancer had already spread to the local lymph glands. Tamoxifen for older women is already saving more lives than any other cancer drug. But, most of the young breast cancer patients who need tamoxifen aren't yet getting it. Even when no measurement had been made of whether or not there were hormone receptors on the original cancer, immediate tamoxifen improved survival.
Tamoxifen also has both bad and good side-effects.
Moreover, this study shows that tamoxifen can halve the risk of a new cancer arising in the other breast. Overall, for women with hormone-sensitive breast cancer, tamoxifen prevents about 30 times as many deaths as it causes. By contrast, for women who have already developed breast cancer the beneficial effects of tamoxifen far outweigh any adverse effects on survival. If all the breast cancer patients who need tamoxifen get it, this will save another 20,000 lives each year. This collaboration brought together detailed information from 55 randomised trials conducted over the past two decades in more than a dozen countries.