Promise & Downfall of Personalized Medicine

I have been talking to various audiences over the past five years about the potential of molecular imaging in the care of our patients. There is no question that the capability to probe processes in the body provides insight that we cannot achieve by anatomic procedures, such as MRI or CT.

I was highly amused when the Society of Nuclear Medicine and Molecular Imaging’s Center for Molecular Imaging Innovation and Translation Past-President Carolyn J. Anderson, PhD, showed a CT scan and challenged the audience to tell whether the image was of a living or dead body. We do not suffer from that limitation in nuclear medicine. Ironically, one of the earliest tests for brain death was scintigraphy-based.

Nuclear medicine was first used to establish function rather than anatomy. As the field has progressed, we have developed better, more specific probes for determining physiology, metabolism and other biologic activity that help to diagnosis and stage the patient. FDG began as a neuroimaging agent only to be disseminated more widely as an oncologic diagnostic agent. We are developing more powerful probes to examine receptor status, and other biomarkers that are critical in defining how we will approach patient treatment. These efforts are directed at making clearer assessments of patient status and determining the efficacy of prescribed care.

Henry R. Wagner, Jr., MD, told us repeatedly: “It’s the phenotype, not the genotype.” The exquisite specificity of a genetic sequence has little information according to information theory. It has to be combined with thousands of other sequences and matched against various diseases to determine what we can conclude from those data. Whereas, we can use an imaging probe to tell a surgeon exactly where the structure is that needs to be removed or repaired; we can tell the oncologist that the treated area is not responding; or we can see if a marker is present or absent that determines a patient’s potential response to treatment.

But there are roadblocks that lie ahead for molecular imaging. First and foremost, these powerful tools are not cheap. The pressure to rein in the cost of medical care works against their introduction and widespread use. Second, we face a public that is increasingly concerned with radiation exposure. This perception works against new imaging exams that involve radiation exposure, which is particularly true for PET procedures with its added dose from particulate emission. Also there is the challenge of finding physicians with adequate training to read and interpret those studies to capture their maximum value.

The challenge to those of us who are champions of molecular imaging is to conduct clinical studies that not only demonstrate sensitivity, specificity and accuracy of the exams but also show a positive impact on the cost of care and improvement in patient outcomes. This challenge is shared by the entire imaging community, not just molecular imagers. We owe it to our patients to provide them with the best information to guide their care.