Clinical Trials Affected by Availability of Participants, Donor Tissues

< July 12, 2006 > -- What if an important cancer clinical trial was set up and nobody came to participate? That scenario could become a reality for cancer researchers across the United States, new research shows.

And another report sounds an alarm about the lack of human eye tissue available for research in the area of ophthalmology.

Cancer Research Short of Participants

Experts say that, for the past few decades, just 5 percent to 10 percent of all cancer patients in the US have joined a clinical trial. But with the current boom in biotechnology and drug development, the demand for willing, eligible study participants now far outstrips the supply.

In a study reported recently at the annual meeting of the American Society of Clinical Oncology (ASCO), Jennifer Tam-McDevitt and colleagues at the Baltimore-based Geriatric Oncology Consortium tallied up the number of participants needed to complete all 679 active phase I, II, and III clinical trials for breast, lung, and prostate cancers in the US.

According to Tam-McDevitt, the nearly 238,000 patients needed to fulfill enrollment and complete these studies "would represent more than half of the total 2005 [cancer] incidence." That number is far greater than the 10 percent of cancer patients currently enrolled in US trials, she says.

"Within certain tumors and certain cancers, we really are running out of patients," warns Tam-McDevitt, who is director of scientific development at the consortium.

Various Factors Affect Trial Participation

Why the shortfall? It is certainly not because patients are unwilling to join up, says Dr. Robert Comis, president of the Coalition of Cancer Cooperative Groups (CCCG), which lobbies to increase patient and doctor participation in trials.

His group presented its own study at the ASCO meeting. It found that, when informed about a clinical trial by their doctor, 40 percent of cancer patients either enrolled or tried to enroll.

Of those people who did meet eligibility requirements and participated, 96 percent said they "were treated with dignity and respect" during the trial, and 91 percent said they would recommend participation to a family member or friend with cancer.

Still, the experts say, some cancer patients do misunderstand clinical trials, worrying that they will be given a placebo "sugar pill" instead of active treatment.

That is never the case, however, since these studies typically compare a newer intervention against the current "gold standard" of care available for their disease.

In fact, clinical trials are usually so well-constructed that patients tend to get better care than they would outside the trial setting, experts say.

Eye Research Running Short of Donors

According to a survey of US members of the Association for Research in Vision and Ophthalmology (ARVO), the major restricting factor in the use of human eye tissue is lack of availability of tissue meeting stringent criteria.

The survey was reported in the journal Investigative Ophthalmology and Visual Science.

The survey's conductor, Christine A. Curcio, Ph.D, of ARVO's Research Tissue Acquisition Working Group (RTAWG), found that only cost exceeded this factor among those surveyed.

Respondents also indicated that local eye banks are the most common tissue source, although most investigators use multiple tissues sources, including remote eye banks, to acquire adequate human eye tissue needed for research.

ARVO states that the availability of human eye tissue for research has been severely impacted by federal regulations and state laws enacted over the last decade Some individual eye bank practices may be of importance on a local level, such as laws prohibiting medical examiners from releasing eye tissue in cases of violent or suspicious death.

The RTAWG believes that the decline in human research tissue may be managed in the short term by researchers working closely with eye banks and other providers, communicating on a regular basis, and clarifying their experimental needs and expectations.

"Nowhere do impediments to obtaining human eyes for research have more impact than in the effort to understand age-related macular degeneration, the leading cause of new vision loss in the elderly," says Dr. Curcio, a professor of ophthalmology at the University of Alabama at Birmingham.

"Macular degeneration, an advanced form of which now has treatment options, still lacks a laboratory animal model that displays the full range of pathology typifying the human disorder. Thus, human tissues are particularly critical."

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