By Brian Carnell

Wednesday, April 17, 2002

A study recently published in the Anals of Oncology evaluated 29 clinical trials conducted to test a drug to treat breast cancer and concluded that a failure to conduct double-blind studies biased the trials by making the drug appear more effective than it was.

In a double-blind clinical trial, neither the patients nor the doctors treating them would know whether or not a given patient is receiving the experimental drug or an existing drug. For something like breast cancer treatment, this is rarely done largely due to the cost of hiring additional doctors to ensure the study remains double blinded.

Of the 29 trials the researchers looked at, only one used a double blinded method (two others involved sending patient records to outside experts for evaluation).

The study argues that the lack of double-blinded studies creates a unique problem for evaluating treatment of conditions such as breast cancer. If a tumor completely disappears, then there is little debate over what happened with a patient. But in many cases, the size of the tumor simply shrinks rather than disappear altogether. According to the study, researchers appeared to overestimate the shrinkage of breast cancer tumors -- almost certainly unconsciously using the knowledge they had of who had and had not received the experimental drug.

The researchers recommend using double-blinded studies wherever these sorts of subjective assessments have to be made, but people who conduct clinical trials argue that while this would be ideal, the cost would be prohibitively expensive.

Source:

Doctors accused of cancer trial bias. The BBC, March 13, 2002.

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