FRIDAY, Oct. 29 (HealthDay News) -- Canadian researchers say they've noticed a disturbing trend: Cancer doctors ordering unnecessary blood transfusions so that seriously ill patients can qualify for drug trials.

In a letter published recently in the New England Journal of Medicine, the researchers report on three cases during the last year in Toronto hospitals in which physicians ordered blood transfusions that could make the patients appear healthier for the sole purpose of getting them into clinical trials for chemotherapy drugs.

The practice raises both medical and ethical concerns, the authors say.

"On the physician side, you want to do the best for your patients," said co-author Dr. Jeannie Callum, director of transfusion medicine and tissue banks at Sunnybrook Health Sciences Centre in Toronto. "If these patients have no other options left to them, you want to do everything you can to get them into a clinical trial," she said.

"But the patient is put in a horrible position, which is, 'If you want in to the trial, you have to have the transfusion.' But the transfusion only carries risks to them," she added.

A particularly serious complication of blood transfusions is transfusion-related acute lung injury, which occurs in about one in 5,000 transfusions and usually requires the patient to go on life support, said Callum.

But besides the potential for physical harm, enrolling very sick people in a clinical trial can also skew the study's results -- making the drug perform worse than it might in patients whose disease was not as far along.

The unnecessary transfusions were discovered by the Toronto Transfusion Collaboration, a consortium of six city hospitals formed to carefully review all transfusions as a means of improving patient safety, Callum said.

At this point, it's impossible to know how often transfusions are ordered just to get patients into clinical trials, Callum said. When she contacted colleagues around the world to find out if the practice is widespread, all replied that they didn't scrutinize the reasons for ordering blood transfusions and so would have no way of knowing.

Dr. J. Leonard Lichtenfeld, deputy chief medical officer of the American Cancer Society, said he was not aware of physicians manipulating eligibility for clinical trials through transfusions. However, the letter raises a provocative issue that should be studied further, he said.

"This is something I have never heard of, never seen and I can't say how common it is," Lichtenfeld said. "I believe the authors have brought a very important issue to the attention of the oncology community and our patients."

If found to be commonplace, Lichtenfeld said the practice should stop. "Giving unnecessary transfusions is not the way we should be increasing access to new cancer drugs," he said.

Another layer to the issue that should be examined, Callum said, is how reasonable the "exclusion criteria" regarding participation in clinical trials are in the first place. The exclusion factors take into account a drug's toxicity and who is likely to be helped, she said.

"Exclusion criteria" are meant to protect patients by keeping people out who are too ill to metabolize a drug effectively, or too fragile to handle its side effects.

But drug companies want positive results, Callum noted, so there can be pressure to select healthier patients to make the drug look better.

If doctors are bypassing the exclusion criteria, it may be that they believe the criteria are unfairly leaving some very sick patients out of trials who could benefit, she said.

"We have to make sure exclusions are not selecting for the best patients that will make the drug look its best," Callum said.

More information

Find out more about blood transfusions at the U.S. National Heart, Lung, and Blood Institute.