Researchers were so excited by early results from a study on preventing the recurrence of breast cancer they halted their work so more women could benefit from the findings.
The study, published online by the New England Journal of Medicine, showed breast cancer patients who followed up five years of tamoxifen treatment with letrozole, an oestrogen suppresser, cut the risk of recurrence by nearly half.
Doctors involved in the study said the findings could benefit hundreds of thousands of women uncertain about what to do after taking tamoxifen, which loses much of its effectiveness after five years. The drug is the top hormonal treatment for oestrogen-fuelled tumours.
“The result has provided women with hope,” said Kathy Anderson, a breast cancer survivor who took part in the study.
The study involved more than 5,000 women in North America and Europe with the most common form of breast cancer who had completed the recommended five years of tamoxifen treatment.
They were given either letrozole or a dummy pill, and results showed that within an average of 2.4 years, 207 had a cancer recurrence - 75 of those on letrozole and 132 of those taking the placebo.
Because of those results, the research was halted so those participants getting the placebo could begin taking letrozole. Publication of the results, which will appear in the journal’s November 6 issue, was moved up because of the importance of the findings.
Letrozole is made by Novartis Pharmaceuticals and sold under the brand name Femara. It paid more than half the cost of conducting the €14m study, and supplied all the letrozole and placebo pills used, officials said.
Doctors who ran the study told a news conference in Toronto, Canada, that the opportunity to help so many women prevailed over the desire for more substantive long-term findings.
“This is available and can provide potentially meaningful reduction in risk of recurrence,” said Dr James Ingle, of the Mayo Clinic in Rochester, Minnesota.
A journal editorial published alongside the study supported the decision.
“At a minimum, suitable patients must be apprised of these important observations and must be given the opportunity to receive letrozole, with an understanding of the limitations of the data,” said the editorial by Dr Norman Wolmark of Allegheny General Hospital in Pittsburgh.
Oestrogen fuels the growth of about half of all breast cancers, especially those in older women.
Tamoxifen is given to almost all such US patients after surgery to help prevent breast tumours from returning.
Tamoxifen, the top treatment to stall tumour growth, prevents oestrogen from linking up to a receptor on the surface of cancer cells.
However, tamoxifen’s effectiveness ends after five years, apparently because the body develops a resistance to it, said Dr Paul Goss of Princess Margaret Hospital in Toronto. He headed the study by 18 doctors from Canadian, US and European hospitals, universities and cancer centres.
Oestrogen pushes dormant tumours to grow, he said, so the study looked at what happened if patients took an oestrogen inhibitor such as letrozole.
Goss and Ingle said further study was required on the effects of prolonged letrozole use. Side effects include increased risk of osteoporosis, hot flashes, night sweats, and pain in the bones, joints or back. Letrozole costs about €5.60 per pill and is taken daily, Ingle said.
Goss said the findings helped him go to work “with a lighter step” because he could tell patients that “yes, something is happening”.
Anderson, a 50-year-old junior school administrator diagnosed with breast cancer more than eight years ago, said she had no idea during the study if she was taking letrozole or the placebo. She said she was relieved to hear earlier this week it was letrozole.
“There is anxiety about recurrence. It fluctuates day-to-day,” she said. “My recurrence rate has just been cut in half.”