Ten years of anti-oestrogens cuts breast cancer recurrence

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Women with breast cancer may receive greater benefit from anti-oestrogens if they take them for twice as long


Postmenopausal women with early breast cancer may receive greater benefit from anti-oestrogens if they take them for ten years rather than the standard five years, research suggests

The risk of disease recurrence and contralateral breast cancer was significantly lower – by 34% – among women who continued an aromatase inhibitor than those who took placebo after five years.

The findings were independent of nodal status, prior chemotherapy and duration of prior therapy with tamoxifen or an aromatase inhibitor, the study authors said.

However, the overall survival rate was not higher with aromatase inhibitors than with placebo, the trial published in the NEJM showed

“The significant benefit in disease-free survival includes not only a numerically larger reduction in events of local, regional, and distant recurrence but also an apparently greater proportional reduction in events of contralateral breast cancer, which may partly explain the absence thus far of an observed overall survival benefit”, the authors wrote.

The double blind, placebo-controlled trial included 1918 women who had previously received around five years of adjuvant therapy with an aromatase inhibitor.

Within two years of completing this initial five-year treatment, disease-free women were randomly assigned to receive 2.5 mg of letrozole or placebo orally once a day for another five years.

The side effects were similar across the placebo and the letrozole treatment group overall.

However, as expected, women taking letrozole for an extended period had a greater incidence of bone-related adverse effects, including loss of bone mineral density and fractures.

So while the prolonged use of letrozole was safe and beneficial, the decision on length of treatment ultimately depended on the patient’s individual risk of disease recurrence and toxic effects, and quality of life, the authors said.

An accompanying editorial said the absence of an overall survival benefit at this time should not be surprising, as the women, who had in most cases entered the trial approximately 10 years after the time of diagnosis, had passed the peak risk of recurrence and a considerable proportion of their remaining risk as well.

“In any event, avoiding a new diagnosis of invasive breast cancer is a benefit in itself”, the editorial said.

“However, the absence of a survival effect will be considered as oncologists and patients with breast cancer weigh the risks and benefits of the use of long-term adjuvant endocrine therapy.”

NEJM 2016, online June 5

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