Italian scientists say the benefits of some cancer drugs may be exaggerated as a rising number of trials are stopped early.
The scientists say drugs hailed as breakthrough treatments for cancer may be less effective and cause more harm than suspected.
The researchers from the Mario Negri Institute for Pharmacological Research in Milan, say data from many of the recent cases had been used to get drug licenses before the long-term impacts were known.
The research team conducted an analysis of 25 drug trials, including some for the breast cancer therapy Herceptin, that were stopped early over a ten year period between 1997 and 2007.
The drugs tested in the trials that were stopped early include some of the biggest new discoveries in cancer therapy, and include Herceptin (trastuzumab) for breast cancer, Avastin (bevacizumab) for bowel and kidney cancer, Campto (irinotecan) for lung and bowel cancer, Sutent (sunitinib) for kidney and gastrointestinal cancer, Nexavar (sorafenib) for kidney cancer, and TaxolCarbo (carboplatin) for ovarian and lung cancer.
Their report shows that of the 25 trials randomly chosen, 14 had been stopped in the past three years, of these, 11 were used to support applications for marketing authorisation from regulators in Europe or the U.S.
Lead researcher Dr. Giovanni Aplone says when a trial is stopped early data on effectiveness and potential side-effects can be missed.
Dr. Aplone suspects the increase in early conclusions to trials suggests that drug firms use good interim results to get their products to market more quickly.
While Dr. Aplone admits that hard evidence to back this claim is scant, he says an in-built bias exists in the system because trials were often only stopped early because the results were positive, when this could just be a "random high", while, those that did not show such positive results were given more time to prove their worth.