AIDSWEEKLY Plus; Monday, August 24 & 31, 1998
Debbara Dingman
"Why don't my patients look like the patients in clinical trials?" asked Melanie Thompson, founder of the AIDS Research Consortium of Atlanta, Georgia, in a presentation to the 12th World AIDS Conference, held June 28-July 3, 1998, in Geneva, Switzerland.
"Reality in 1998 differs significantly from the expectations raised by clinical trials," Thompson said. "Clinical experience outside clinical trials has not reproduced the very high rates of viral suppression nor the durability of response seen in the selected group of patients studied in the pivotal trials leading to drug licensing."
Clinical trial patients live 66 percent longer and have fewer opportunistic infections than non-trial patients, independent of treatment, stage of disease, and CD4(+) cell count.
"Half of what we taught you is wrong, unfortunately we don't know which half," quipped Thompson. "Clinical trials do not accurately reflect clinical reality."
Thompson proposed four causes for the differences found between the clinical trial and general populations:
* Healthier patients are selected for clinical trials.
* Participation in clinical trials is therapeutic.
* Studies differ in design.
* Studies differ in methods of data analysis.
"Restrictive entry criteria introduce selection bias into clinical trial populations," Thompson said.
Clinical trials screen out patients who are taking other medications or who have active opportunistic infections, substance abuse, liver enzymes, mental illness, or dementia. But once patients enter a trial, they often receive significantly better overall health care.
"Participation in clinical trials may indeed elevate the standard of care offered to a patient," Thompson said.
Clinical trials often provide child care and transportation for enrolled patients. They may be paid for their office visits. They get more staff attention and their side effects and toxicities are managed more aggressively. They receive more support for drug compliance.
Differences between studies make generalization to the real clinical world difficult. From one study to another differences may be found in population, entry criteria, visit schedule, study endpoint, and assay used.
"Drugs are licensed on short term data but patients have long-term needs," Thompson said.
She also noted that statistical analyses of clinical trial results may exaggerate the effectiveness of a drug in clinical practice. She presented the differences between results of on-treatment and intent- to-treat analyses, showing a 20 percent difference in response.
Thompson proposed caution in interpretation of clinical trial results.
"In the end, our patients will keep us honest, and we owe it to them to challenge ourselves to think critically as we try to apply new findings to clinical care," she concluded.
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