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Improving Health Through Medical Physics

AAPM comments at the Federal Coordinating Council for Comparative Effectiveness Research Listening Session on May 13, 2009.

June 11, 2009

This statement is being given on behalf of the American Association of Physicists in Medicine (AAPM), which represents over 6,700 medical physicists. AAPM’s mission is to advance the practice of physics in medicine and biology by encouraging innovative research and development, disseminating scientific and technical information, fostering the education and professional development of medical physicists, and promoting the highest quality medical services for patients. Medical physicists contribute to the effectiveness of radiological imaging procedures by assuring radiation safety and helping to develop improved imaging techniques (e.g., mammography, computed tomography, magnetic resonance imaging, ultrasound). Medical physicists contribute to the development of therapeutic techniques (e.g., prostate implants, stereotactic radiosurgery), collaborate with radiation oncologists to design treatment plans, and monitor equipment and procedures to insure that cancer patients receive the prescribed dose of radiation to the correct location.

The Department of Health and Human Services states that: “Comparative effectiveness research provides information on the relative strengths and weakness of various medical interventions.” Various alternative medical procedures and/or technologies may be capable of achieving a given medical intervention. Thus, it is necessary to compare these medical procedures for specific groups of patients to optimize the benefit (e.g., earlier detection of cancer in screening procedures; improved targeted dose delivery in radiation therapy) and minimize the cost and/or risk (e.g., reduced radiation dose in diagnostic procedures; minimization of dose to normal tissues and critical organs in therapeutic procedures). Means to perform such comparative assessment studies may include clinical evidence-based outcomes evaluations that require expensive and sometimes lengthy clinical trials involving a substantial number of patients to achieve statistical certainty. However, when well-defined physical or engineering differences exist between products, which do not rely on different anatomic or physiological phenomenon, comparative effectiveness can be determined by assessing technology using quantitative metrics. This will be particularly useful and cost effective in situations where simple modifications of an existing medical technology are introduced or a new technology is available that is changing rapidly in its potential for proving efficacy. In those cases and at those times, relatively inexpensive physical measurements or observer-based diagnostic accuracy studies may be most appropriate.

Examples of ongoing and future roles of medical physics in comparative effectiveness studies include optimization of radiation dose in computed tomography (CT). Image quality can be assessed quantitatively between different computed tomography (CT) scanners at the same radiation dose levels, providing an objective measure of comparative effectiveness that may not require a clinical trial. Another example is the comparative evaluation of mammography, breast CT, and breast tomosynthesis in detecting and assessing the extent of breast cancer by using various metrics of physical and psychophysical image quality (e.g., spatial resolution, noise, or conspicuity) and balanceing the results in terms of cost and radiation dose level. Another example is the comparative effectiveness of photon therapy versus proton therapy in the treatment of prostate cancer by measuring the dose to the tumor target compared to the rest of the patient’s (normal) tissues. In all these situations, comparative effectiveness can be ascertained without “costly” clinical trials, or in advance of such trials.

It is important to note that comparative effectiveness studies are necessary in diagnostic exams (e.g., screening, detection, diagnosis, risk assessment), as well as in therapeutic procedures (e.g., response to therapy, radiation treatment planning). Medical physicists collaborate with other medical professionals and are integral to the development, evaluation, and implementation of technology and procedures in medical imaging and in the therapeutic use of radiation. These activities provide a basis for objective comparative effectiveness for the underlying technology in medical procedures.

In summary, it is important to realize that technology assessment studies are a subset of comparative effectiveness studies, that the reach of comparative effectiveness includes both diagnostic and therapeutic procedures and systems, and that medical physicists play a vital role in conducting such studies.