Can Molecular Imaging Usher in Personalized Medicine?

I have been struggling recently with the notion that genomics is going to revolutionize our ability to diagnose and treat disease. Why? A basic tenet of information theory is simple: the more precisely you can measure something, the less information it contains. Think about that statement in the context of sequencing the genome. How much more precise can one be in identifying the order in which nucleic acids make up the DNA? One must sequence numerous DNA samples to draw conclusions about the implications of that sequence relative to a disease. One must determine what is normal and how that is represented in the DNA sequence. Then, one must determine where the genome changes in the case of disease and the strength of that correlation. A further level of complexity is to establish at some early point what the genome sequence is in the normal individual versus when he or she presents with a disease or symptoms.

In contrast, when a patient presents with symptoms of a disease, the diagnostician employs imaging when there is information that needs to be established to differentially diagnose or assess disease progress. It is real-time information that a trained imaging physician can use to help the patient.

The challenge of those employing molecular imaging is to bring new compounds to market. As we have seen in pharma’s development of new drugs, many of the easiest challenges have already been met. And so, we are trying to use imaging to get information on diseases that occur less frequently and thus present less opportunity to generate a return on investment. Compounding this problem is the pressure being exerted to control the cost of healthcare as well as reduce radiation exposure, evidenced by the current effort to secure adequate reimbursement for Lymphoseek.

As we see more agents labeled with radiofluorine or radiocarbon and imaged with PET that can interrogate specific molecular pathways, the likelihood that these radiopharmaceuticals will be brought into practice is diminishing. Compounding this problem is the special exception that was given to oncologic imaging agents that is not shared with agents for imaging cardiac, neurologic or other diseases besides cancer. With some justification, the referring physician community is demanding new agents be supported by clear evidence of value to the patient. As well, CMS makes the same demands to justify reimbursement for the procedure. Third-party insurers generally follow CMS in what procedures are covered.

I firmly believe that personalized medicine will depend entirely on the ability of the molecular imaging community to demonstrate the power of the radiopharmaceuticals in the care of each patient. Identifying those instances in which a drug or treatment is failing to help the patient provides an economic and health benefit to that patient. Moving that patient to a different, potentially more beneficial treatment has to be attractive to insurers as well as the patient. Using imaging to demonstrate that a patient has the receptors or other biomarkers that are effective targets for some intervention is another benefit that cannot be dismissed. It is unlikely that genomic sequencing will ever be able to compete since there has to be an invasive procedure to get a sample for sequencing from a tumor or other target organ. Now, the responsibility is on the molecular imaging community to exploit the advantage that imaging provides and to direct the conversation to the need to incorporate more imaging in patient care, not less.