New data suggests positive benefits in switching treatment for breast cancer patients

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New data presented at a major international breast cancer conference1 indicate that post-menopausal women with early breast cancer who have their adjuvant therapy changed from tamoxifen to anastrozole, are less likely to experience a relapse of the disease than those who remain on tamoxifen. Furthermore, women who have their therapy changed are less likely to suffer from a serious drug-related side effect. These promising data are from the landmark ITA (Intergruppo Tamoxifen Arimidex) trial involving 449 Italian patients with hormone sensitive early breast cancer. These results provide further evidence that there is now a highly effective and better-tolerated treatment alternative to tamoxifen for post-menopausal women with early breast cancer.

The results from the ITA study suggest that, in addition to better disease-free survival, women already receiving tamoxifen, the current gold standard, who switched their treatment to Arimidex¨, were less likely to suffer from serious side effects commonly associated with tamoxifen, such as blood clots or endometrial cancer, than those women who continued to take tamoxifen.

In discussing these new findings, Professor Jeffery Tobias, University College Medical School and University College Hospitals, London, England, commented, “In my view, these new data are extremely important. They imply that patients already taking tamoxifen may also be candidates for treatment with anastrozole and this is the first time we have been in a position to make such a statement. These data certainly add to the growing body of evidence supporting the use of anastrozole in the adjuvant setting.”

Following surgery to remove a breast tumour, women are usually given a hormonal treatment known as adjuvant therapy, for a period of five years, to help prevent the breast cancer from returning. Although tamoxifen revolutionized the treatment of breast cancer when it was launched over 25 years ago, it is unfortunately associated with a number of serious side effects, such as endometrial cancer, deep vein thrombosis and stroke.

In 2001, the first results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, a clinical trial comparing tamoxifen with a newer drug, Arimidex¨, were published. Results of this study, involving over 9,300 patients worldwide, showed that in post-menopausal women with newly diagnosed, early breast cancer (meaning those women who were not already taking a hormonal treatment), Arimidex¨ was more effective than tamoxifen in preventing the return of the cancer, and was less likely to result in serious side effects. As expected, based on the pharmacology of both treatments, the tamoxifen treated group did show tolerability benefits in terms of musculoskeletal disorders and fractures.

Based on the ATAC trial results, Arimidex® has been approved as an adjuvant treatment for post-menopausal women with hormone receptor-positive early breast cancer in 26 countries, including the USA, UK, Japan, Australia, Switzerland, Germany, and Spain. Arimidex¨ is currently under review by Health Canada for use as an adjuvant treatment of early breast cancer.

There remains, however, a large number of women who were prescribed tamoxifen before these results became available and are now part way through their recommended five-year treatment course. Until now, there has been no evidence to indicate whether they would be better off changing their therapy to the newer drug or they should continue taking tamoxifen. The latest ITA trial results represent the first and only data needed to answer this important question.