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product registration, and the patient eligibility criteria are so narrow for these trials that they do not really provide guidance to the physician about the population he or she is treating. “We need to realize that clinical trials and the kinds of evidence that we tend to consider to be the gold standard are not particularly good at guiding clinical practice,” he said.

Amy Abernethy, associate professor of medicine at Duke University School of Medicine, noted that once a drug enters the market for a FDA-approved indication, it is typically used more broadly for other indications. Off-label use12 is exceptionally common in oncology, with the NCCN estimating in 2005 that half to three-quarters of all cancer prescriptions were written for off-label indications, Abernethy reported. Such off-label prescribing is common in oncology because of the life-threatening nature of the illness, and the biologic plausibility that what works for one type of cancer might work for a similar cancer. Furthermore, once drugs enter the market based on efficacy for a narrow group of cancer patients, pharmaceutical companies are not likely to invest in more Phase III clinical trials to broaden that use, Abernethy said.

In addition, reimbursement by insurers fosters off-label prescribing. “Off-label prescribing in oncology is a real part of care and a substantial contributor to cost that is reinforced by the compendia-based reimbursement mechanism that tries to review rapidly evolving evidence and information without a mechanism to make sense of it all,” said Abernethy. “We need a strategy to define appropriate off-label use. It’s the Wild Wild West out there and we have not demanded that we figure out a way to make sense of it” (see Figure 10).

Abernethy said that drug compendia, such as the NCCN, often guide the use of off-label prescribing of cancer therapeutics and the reimbursement for such regimens (Abernethy et al., 2009). However, compendia are not designed for this purpose, nor are they designed to guide the choice of one drug compared to another drug (Abernethy et al., 2010a). “We are relying on the compendia system to help us essentially do comparative effectiveness research, but really their role still in their minds has been that of helping to understand toxicity around drugs, and what does it mean once a drug has been prescribed,” Abernethy said.

Abernethy found a number of subjective processes influenced the validity of the assessment, choice of citations, and the policy for equivocal evidence


12Off-label use is the prescribing of drugs already on the market for an indication, age group, dose, or form of administration that has not been approved by the FDA.

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