Adjuvant tamoxifen - longer against shorter
Reliable assessment of the efficacy and safety of prolonging the use of
adjuvant tamoxifen: a large, simple, randomised study.
Adjuvant tamoxifen therapy in early breast cancer:
Existing evidence
Trials of adjuvant tamoxifen in women with early breast cancer have demonstrated
a highly significant improvement in 10-year survival. However, it is not
yet known how long women with early breast cancer should continue to take
adjuvant tamoxifen. Most trials of tamoxifen versus no tamoxifen involved
only 1, 2 or 5 years of tamoxifen. Within this range, the more prolonged
treatments appear more effective at preventing or delaying recurrence and
improving 10-year survival. However, among women who have already had
some years of treatment there is no reliable evidence, from direct randomised
comparisons of different durations, of an extra therapeutic advantage from
more prolonged treatment. Moreover, while tamoxifen has relatively
few short-term or medium-term side-effects (particularly for post-menopausal
women), it produces some increase in the incidence of endometrial cancer,
and may have some other important long-term side-effects. These risks may
increase if the drug is taken for many years. Hence the balance of benefits
and risks of long-term tamoxifen needs to be determined reliably.
If longer tamoxifen improves survival by just
a few percent, reliable demonstration of this benefit could save thousands
of lives each year
Even if longer-term tamoxifen is somewhat more effective than just a few
years of treatment, the net advantage is likely to be only moderate. For
example, five additional years of treatment would be unlikely to improve
the 10-year survival by more than a few percent, and might not improve
it at all. Indeed, if longer treatment produces extra side-effects and
little extra benefit, it might even make the 10-year survival slightly
worse. Breast cancer is so common that reliable demonstration of just a
small benefit or just a small hazard could save thousands of lives worldwide.
Even a null result in a study big enough to be reliable would avoid
the unnecessarily prolonged treatment of many hundreds of thousands of
women each year.
Publication of the final results of the Atlas study will be
in the names of the many collaborators, not the central organisers, and
the chief acknowledgement will be to the patients themselves.
The aim of Atlas is to assess reliably the balance
of risks and benefits in prolonging the duration of adjuvant tamoxifen
by at least 5 extra years.
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