AstraZeneca’s Nolvadex (tamoxifen) could lose its crown as the standard treatment for hormone-receptor positive breast cancer patients post-surgery, according to a new analysis from Datamonitor, which claims that the newer aromatase inhibitors are increasingly being used in place of tamoxifen.

The report claims that almost two-thirds of early-stage breast cancer patients currently receive the anti-hormonal drug, tamoxifen, after surgery, but data showing that aromatase inhibitors are more effective in increasing survival and minimising disease recurrence has prompted a surge in their use.

However, the news remains good for the Anglo-Swedish firm, with Datamonitor expecting that its new offering, Arimidex (anastrozole), which belongs to the aromatase inhibitor class that works by lowering the oestrogen level in the body, will supersede tamoxifen and become the gold-standard adjuvant therapy for local and locally advanced breast cancer. Arimidex is already more commonly used in the post-operative setting in the US and France compared with tamoxifen. Datamonitor believes that other markets will also begin using Arimidex more often after data published at the end of last year showed that five-years of treatment with AstraZeneca’s drug was more effective than the standard five-year tamoxifen therapy in terms of survival [[09/12/04b]].

Other aromatase inhibitors, such as Novartis’ Femara (letrozole) and Pfizer’s Aromasin (exemestane), are already on the market, but the analysis notes that they are less commonly used, primarily due to a lack of long-term clinical data. In addition, Datamonitor claims that these drugs will remain peripheral therapies as neither Novartis nor Pfizer has the experience and expertise of marketing anti-hormonal therapies like AstraZeneca, which also has Faslodex (fulvestrant), Zoladex (goserelin) and Casodex (bicalutamide) in its portfolio.

Breast cancer is the most common malignancy that afflicts women, with more than 420,000 new cases expected to be diagnosed in the seven major markets in 2005. However, it remains a disease that is highly curable if diagnosed at early stage.