News Release

Letrozole shows long-lasting survival benefit compared with tamoxifen in patients with most common type of breast cancer

Peer-Reviewed Publication

The Lancet_DELETED

In the long term, the aromatase inhibitor letrozole is more effective at preventing the return of breast cancer and significantly improves survival time compared with tamoxifen in postmenopausal women with hormone receptor-positive early breast cancer, according to the 12-year results of the Breast International Group (BIG) 1-98 study published Online First in The Lancet Oncology.

"At a median follow-up of over eight years, women given letrozole monotherapy after surgery for five years had a 20% reduced risk of their breast cancer coming back and were 21% less likely to die compared with women given tamoxifen alone. This updated analysis shows that letrozole offers long-term protection over tamoxifen in these patients"*, explains Meredith Regan from the International Breast Cancer Study Group Statistical Center at Dana-Farber Cancer Institute, Boston, USA, one of the lead authors on the study.

Aromatase inhibitors (AIs) are now part of standard treatment after surgery for most postmenopausal women with oestrogen-receptor positive tumours, which make up around 60% of all breast cancers. Currently, AIs such as letrozole are given alone or in sequence with tamoxifen.

The BIG 1-98 trial enrolled 8010 women, and was designed to make two comparisons—5 years of letrozole with 5 years of tamoxifen (4922 women), and 5 years of letrozole with sequential treatments of two years of one of these drugs followed by 3 years of the other (6182 women). The first results of the trial were presented in 2005 and updated analyses were planned every 2 years in recognition of the persistent and long-term risk of relapse and death in these women.

At this update, 12 years since the first patient was enrolled in the BIG 1-98 trial, there was a 32% increase in the number of relapses compared with the previous ten-year update (2074 relapses vs 1569 relapses).

With long-term patient follow-up averaging more than 8 years, 5 years of daily letrozole monotherapy reduced both the risk of relapse and the chances of dying after breast cancer by at least a fifth compared with tamoxifen treatment alone.

For the second comparison, neither sequential treatment—tamoxifen followed by letrozole or letrozole followed by tamoxifen—significantly decreased the likelihood of relapse or death compared with letrozole monotherapy.

The authors conclude: "This update of BIG 1-98 at 8.1 years median follow-up reinforces the evidence that letrozole monotherapy is better than tamoxifen in controlling breast cancer recurrence and improving survival for postmenopausal women with endocrine-responsive early breast cancer."

They add: "Sequential treatments involving tamoxifen and letrozole do not improve outcome compared with letrozole monotherapy, but might be useful strategies when considering an individual patient's risk of recurrence and treatment tolerability… overall risk and tradeoffs with respect to side-effects and other burdens will influence the preferred choice of treatment."

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Dr Meredith Regan from the International Breast Cancer Study Group Statistical Center, Dana-Farber Cancer Institute, Boston, Massachusetts, USA. T) +1 617 632 2471 E) mregan@jimmy.harvard.edu

Notes to Editors: *Quote direct from author and cannot be found in text of Article.


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