Precision Imaging: The Next Frontier
Radiology’s next great advancement is as small as the cells in our bodies.
Inrecent years, Angelina Jolie has made headlines with a series of New York Times op-eds detailing her efforts to avoid developing cancer. In 2013, the Oscar-winning actress, whose mother, grandmother, and aunt all died of cancer, wrote that she had a mutation of the BRCA1 gene and detailed her decision to have bilateral mastectomy. In 2015, she published another op-ed about her decision to have bilateral salpingo-oophorectomy.
But what if we lived in a world where none of her procedures had been necessary? What if the growing number of women electing to undergo mastectomies in the U.S. could have undergone a highly targeted form of treatment that stopped the cancer the moment it was detected? This may sound like science fiction, but it is the promise of a new approach to patient care gaining acceptance within both radiology and the wider medical community.
Finding the Phenotype
Precision imaging is a relatively new concept that’s built on the foundation of precision medicine. In a 2011 white paper, the National Research Council of the National Academies defined precision medicine as “the tailoring of medical treatment to the individual characteristics of each patient.”4 As an off-shoot of precision medicine, precision imaging can be used to combine data about a patient’s clinical phenotype and genotype/gene expression. (See “Glossary of Terms.”) Doing so can help categorize patients into subgroups based on similar clinical presentation and disease biology.
Phenotyping patients is something radiologists have been doing since the beginning, argued James H. Thrall, MD, FACR, chair emeritus of the department of radiology at Massachusetts General Hospital in Boston, during a recent interview. Only, he said, radiologists haven’t traditionally thought of themselves as experts at subcategorizing patients in this manner. During his Moreton Lecture at May’s ACR 2015™ meeting, Thrall said it is high time radiologists shift their thinking.
“Although it has never been articulated explicitly in the past,” noted Thrall, “radiologists are fundamentally in the business of creating imaging phenotypes through their systematic application and analysis of imaging studies, enumeration of findings, and the application of grading, scoring, and classification systems linked to their findings.”5
Why is this type of disease categorization significant to the future of the specialty? One of the most important reasons, said Thrall in a recent JACR® article, has to do with clinical trials. “Imaging methods play a key role in categorizing patients into subpopulations for clinical trials through scoring and classification systems,” Thrall explained. “These systems establish imaging phenotypes that distinguish important characteristics between patients such as relative prognosis and likelihood of benefitting from a particular therapy.”
A Tailored Approach
Giles W. Boland, MD, FACR, professor of radiology at Harvard Medical School and vice chair of business development at Massachusetts General Hospital Cancer Center, agrees that precision imaging can play a big role in selecting patients for clinical trials. “Right now, clinical trials are clunky from an imaging perspective,” said Boland. “We often use generic CT scanning or MRI depending on the particular patient or disease, or we may use plain film. Using a generic test, for want of a better word, to image a particular subtype of disease is not very precise. More precise imaging techniques identify, delineate, and quantify the extent of disease better. They can often be the earliest predictors to the likely patient response and outcome to specific therapies and can, in some circumstances, predict the genetic mutation responsible for the disease.”
In Boland’s estimation, precision imaging will see radiologists collaborating with pharmaceutical companies from the ground up to discern which modalities and tests are most likely to yield useful information for each particular subset of patients. “We’re going to tailor the imaging to the question being asked,” stated Boland.
“Clinical trials with pharmacological drugs should be married to precision imaging in the context of specific molecular targets (e.g., proteins found only on the surface of cancer cells),” said Sam Gambhir, MD, PhD, chair of radiology, professor of clinical investigation in cancer research, and professor of bioengineering and materials science and engineering at Stanford University. During clinical trials, he asked, why not customize the imaging so that it’s matched to the particular drug or treatment in question?
“For example,” said Gambhir, “if I have a drug that is used to treat lung cancer, and the drug affects a specific receptor only found on lung cancer cells, then the imaging for this patient isn’t only a CT scan. It’s a PET scan that measures that same receptor that the drug interacts with.” So instead of watching the tumor either shrink or not shrink, concluded Gambhir, the radiologist could ascertain that the drug is working because it’s occupying the receptor it’s designed to hit.
The benefits of this level of precision are myriad. “We can use precision imaging to help more effectively identify, evaluate, and monitor patient subpopulations,” asserted Boland. “And maybe as a result, a given clinical trial can be reduced from five years to two years.” This would mean a significant reduction in cost to the pharmaceutical companies, not to mention major benefits to patients who would gain access to new drugs more quickly.
Communication Is Key
Beyond helping select patients for clinical trials, radiologists can also utilize imaging phenotypes to make diagnoses, estimate the severity of a disease, and track a patient’s prognosis. However, according to Thrall, to accomplish all of this, radiologists need to communicate clearly so that everyone in the care pathway understands each other. Since many referring clinicians use words associated with precision medicine, this means that radiologists should update their lexicons, replacing antiquated terms like “Roentgen signs” with more updated terms like “imaging biomarkers.” (See “Glossary of Terms.”)
For radiology to enter the precision imaging era, radiologists must bring more to the table than simply interpreting scans. Understanding the clinical significance of findings and leveraging this knowledge to influence the course of treatment is the future of imaging. It is time for radiologists to begin thinking of themselves as the physicians most equipped to subcategorize patients and monitor their treatment on a molecular level.
Note: Click the glossary below to enlarge.
By Chris Hobson, Senior Communications Manager, Imaging 3.0™