Unpublished data shows breast cancer drug 'third less effective'

Drug trial involving 1,000 women given Herceptin shows drug is not effective as thought

Unpublished data from trials of the breast cancer drug Herceptin show that it may be up to a third less effective than has been claimed, experts will say today.

Writing in the Lancet medical journal, doctors in New Zealand say they may have identified a new case of publication bias - in which drug companies publish only trial results that are favourable.

Doctors from the Pharmaceutical Management Agency (Pharmac), which is the equivalent of the UK's National Institute for health and Clinical Excellence, say the missing data is important and relates to a trial involving nearly 1,000 women.

In the trial, the North Central Cancer Treatment Group (NCCTG), one group of women with early breast cancer were given Herceptin at the same time as chemotherapy drugs called taxanes. Another group were given Herceptin after they had finished chemotherapy.

The results from those given Herceptin and taxanes concurrently have been published, say the New Zealand team, and were good - they cut the number of breast cancers that recurred by a third.

But results from the women who were given taxanes followed by Herceptin (the method used in Britain) have not been published in a peer-reviewed journal. The experts are aware of both results, as they featured in an oral presentation at a cancer meeting in 2005 and on a slide presentation on a website.

What they show, say the Pharmac doctors, was that only a comparatively small number of cancers were prevented from coming back and, statistically, there was a reasonable chance that Herceptin did not protect the women at all.

"The selective release of data from the NCCTG study has far-reaching implications for women with [Herceptin-susceptible] early breast cancer. Without these data, sequential trastuzumab (Herceptin) seems more effective than it probably is," write Dr Scott Metcalfe and his colleagues at Pharmac. With the missing data the trial "shows a treatment effect one-third less than initially estimated," they add.

Another big Herceptin trial, called Hera, looked at the use of the drug following chemotherapy instead of at the same time and had very positive results. In New Zealand, Pharmac tells doctors to give it at the same time as a taxane.

Roche, the maker of Herceptin, said the NCCTG trial was sponsored by the National Cancer Institute in the US. There was a pre-agreed trial protocol and an independent monitoring committee oversaw the results. It was up to the investigators to publish the data, said Roche, adding: "Four large trials involving more than 13,000 patients have consistently shown that Herceptin extends survival when administered either sequentially or concurrently with adjuvant chemotherapy."

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Sarah Boseley, health editor

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