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component of any clinical trial. Unlike frequentist methods, Bayesian methods
assign anything unknown a probability using information from previous experi-
ments. In other words, Bayesian methods make use of the results of previous experi-
ments, whereas frequentist approaches assume we have no prior results. This
approach is being put to the test at M. D. Anderson Cancer Center (Houston, TX),
where more than 100 cancer-related phase I and II clinical trials are being planned
or carried out using the Bayesian approach. The Bayesian approach is better for
doctors, patients who participate in clinical trials and for patients who are waiting
for new treatments to become available. Physicians want to be able to design trials
to look at multiple potential treatment combinations and use biomarkers to deter-
mine who is responding to what medication. They would like to treat that patient
optimally depending on the patient’s disease characteristics. If interim results indi-
cate that patients with a certain genetic makeup respond better to a specifi c treat-
ment, it is possible to recruit more of those patients to that arm of the study without
compromising the overall conclusions. Use of the Bayesian approach may make it
possible to reduce the number of patients required for a trial by as much as 30 %,
thereby reducing the risk to patients and the cost and time required to develop thera-
peutic strategies.
Using a Bayesian approach, contrary to the standard approach, the trial design
exploits the results as the trial is ongoing and adapts based on these interim results.
In order to have the personalized medicine, it will be necessary to be more fl exible
in how we evaluate potential new treatments. Moreover, it is possible to reduce the
exposure of patients in trials to ineffective therapy using the Bayesian approach.
Whether the Bayesian approach will gain acceptance in clinical trials depends a lot
on its acceptance by the FDA in determining safety and effi cacy of new treatments.
The FDA has already approved the Bristol-Myers Squibb drug Pravigard Pac for
prevention of secondary cardiac events based on data evaluated using the Bayesian
approach.
Concluding Remarks
The important points of role of biomarkers in development of personalized medi-
cine are:
- Biomarkers will enable early diagnosis of disease to facilitate optimization of
therapy. - Biomarkers will play an important role in combining diagnosis with therapeu-
tics − an important feature of personalized medicine. - There will be an increase in the number of new drugs suitable for personalized
treatment, which will be discovered by use of biomarkers. - Validated biomarkers will play an increasing role in clinical trials for personal-
izing therapeutics. - Biomarker-based monitoring of drug effi cacy will guide personalized manage-
ment of several diseases.