Great Expectations: PET/CT Delivers

More than five years after PET/CT technology thrust open the door to clinical molecular imaging, the technology is now proving its clinical worth. As the National Oncologic PET Registry (NOPR) releases data collected over the last two years, the value of PET/CT in oncology patient management is clear.

The NOPR, designed to examine the role of PET in management of cancers not currently eligible for Medicare coverage, points to the value of PET/CT imaging. “Based on the data, we can expect PET/CT results to change patient management in about 35 percent of cases,” states Chaitanya Divgi, MD, chief of nuclear medicine and clinical molecular imaging at the University of Pennsylvania Health System in Philadelphia. If the Centers for Medicare & Medicaid Services (CMS) accept the data, PET/CT access should improve, says Todd Blodgett, MD, chief of cancer imaging at University of Pittsburgh Medical Center (UPMC) in Pennsylvania.

PET/CT is spreading it wings beyond oncology, too. The hybrid modality is a boon to cardiac imaging, providing a solid option for an array of cardiovascular imaging needs. This month, Health Imaging & IT visits a trio of experts to learn more about molecular imaging’s premiere modality.

Oncology imaging: Removing barriers, new frontiers

Oncology imaging is the major growth area for PET/CT imaging. The publication of NOPR data could open the door to applications in scores of additional cancers. “NOPR applies to staging and re-staging of any malignancy currently not covered by Medicare or a third-party payor,” explains Blodgett. The significance is tremendous because the lack of reimbursement has limited PET/CT imaging.

Although reimbursement policies vary by state, in many cases payors do not reimburse for PET/CT without a previous diagnostic CT study. If the CT results are normal, it can be difficult to persuade an oncologist to order a PET study. Reimbursement woes cross paths with a second barrier—physician education. 

“Even in the United States where PET/CT systems are ubiquitous, PET/CT is underutilized because many physicians think CT is the gold standard. But CT often misses lesions that are detected with PET or PET/CT,” notes Blodgett. If the CT is abnormal, the oncologist may use the CT for decision-making; however, baseline PET/CT studies are critical and can change the overall approach to patient management. Take, for example, lung cancer patients. “There is no low-risk lung cancer. A patient should not be referred to surgery if occult metastatic disease is present,” says Blodgett. And PET/CT, rather than CT, is the best means to locate occult disease.

“The reimbursement paradigm needs to be reversed,” states Divgi, with simultaneous PET/CT serving as the gold standard for staging and treatment efficacy monitoring. As the reimbursement climate changes, PET/CT providers and radiologists need to address other barriers to more widespread use of PET/CT imaging. “It’s critical for radiologists to interact with our oncology colleagues to make sure they understand the appropriate role of PET/CT,” continues Divgi. In other words, radiologists need to make time to attend tumor boards and multi-disciplinary conferences, where they can educate colleagues about the value of PET/CT imaging. Another key piece of the puzzle is the clinically relevant report. The report should describe areas of increased uptake and SUV and include clinical interpretations that can guide cancer patient management.

On the oncology horizon

Treatment efficacy monitoring or response to therapy could be the next major PET/CT application. “It appears that physicians should be able to predict whether or not a therapy is working earlier with PET/CT than with CT alone,” explains Blodgett. Currently, PET/CT is approved only for therapeutic monitoring of breast cancer patients. “As more therapeutic options become available for different types of cancer, it’s important to employ PET/CT imaging for therapeutic monitoring,” continues Blodgett. That’s because physicians can switch a patient’s therapy if the PET/CT data show that the patient is not responding to the first-line therapy.

Divgi of the University of Pennsylvania Health Center believes treatment efficacy monitoring could see significant growth in the next few years. Currently, Divgi’s department completes about 16 PET/CT studies daily on its Philips Healthcare Gemini Time of Flight PET/CT scanner. About 20 percent of studies are staging studies, another 20 percent are ordered to evaluate patients for recurrence, and the final 60 percent of studies monitor treatment efficacy.

Another growing oncology application is radiation therapy planning. PET/CT offers the same type of benefits for radiation therapy treatment planning as it does for other diagnostic situations, says Blodgett. That is, PET/CT detects more lesions than anatomical imaging modalities, and it helps radiologists better delineate the borders of the tumor. “If we’re going to irradiate a lesion, we need to see it,” sums Blodgett. For example, consider a lung cancer patient with a lesion pressing on a bronchi. The lung could collapse around the tumor, making it impossible for the radiologist to determine where the tumor ends and the collapsed lung begins on a standard CT study. A PET/CT study, on the other hand, provides the anatomical and functional data needed to delineate the lesion and develop a treatment plan that avoids critical and fragile areas. 

Sites that plan to incorporate PET/CT into the radiation therapy treatment planning process need to carefully consider equipment. UPMC uses a GE Healthcare Discovery PET/CT scanner. An additional radiation therapy treatment planning package includes a flat table, so patients can be scanned in the relative treatment position. In addition, the wide bore scanner accommodates additional radiation therapy positioning devices.

Versatility unveiled: expanded cardiac applications

Although PET/CT seems synonymous with oncology imaging, the hybrid scanner is not relegated to a sole specialty. A number of sites across the country have deployed cardiac PET/CT and realized a number of advantages including cost-savings and accelerated decision-making and patient treatment.

Take, for example, Emory: Crawford Long Hospital in Atlanta. The cardiovascular imaging department installed Siemens Medical Solutions Biograph 64 PET/CT camera in June 2006 and uses it to scan about 300 cardiac patients monthly. “PET/CT is our first choice for evaluating patients with chest pain. We use it for inpatients, outpatients and in-between patients,” says Randolph Patterson, MD, director of cardiovascular imaging at Emory: Crawford Long Hospital and Professor of Medicine [Cardiology] at Emory.

The hospital has seen major benefits in its “in-between” or ED patient population. “PET/CT saves time and money with ED patients. Previously, patients who presented to the ED with chest discomfort were admitted for two to three days of testing. Now, they can be placed in a Clinical Decision Unit, undergo a PET/CT study and can be released in less than 24 hours if the test is normal,” explains Patterson. “PET/CT is a more sensitive and more specific test for infarction and ischemia than SPECT, and it’s quick and safe.”

The cardiovascular imaging department turns to the PET/CT camera for a number of other indications as well. If an outpatient undergoes an equivocal SPECT or stress echo, the cardiologist can turn to PET/CT to clarify the diagnosis. In other cases, a post cardiac catheterization PET/CT can be used to review borderline lesions and determine whether the patient needs stenting, angiography or surgery. Finally, an FDG PET/CT study helps physicians assess cardiac viability; by determining how much live tissue is present the cardiologist can better determine if a patient will benefit from surgery or angiography.

The five-year plan

PET/CT is in a state of evolution with the modality proving its utility in more oncology applications and offering new options in cardiovascular imaging. The modality is expected to continue to evolve in the longer term, too, with external factors opening new doors.

“The entire future of PET/CT is in tracer development. The scanner technology is mature, but we continue to rely on a single tracer for most applications,” says Blodgett. In the future, new tracers could target specific cancers. The downside is time. Blodgett predicts the next major oncology tracer is five to 10 years away from clinical practice.

The situation is similar in cardiac PET/CT imaging. “We’d love to see other tracer options,” says Patterson, “especially one that targeted vulnerable plaque.” It may be possible to image vulnerable plaque, the culprit in nearly half of all myocardial infarctions, with FDG PET/CT; however, researchers are confident that another tracer will concentrate more intensely in arteries impacted by vulnerable plaque to produce a more accurate image of the patient’s condition. Another area for improvement is blood flow measurement. Currently, PET/CT images relative blood flow to the heart. If the scanner could produce data about absolute blood flow, it would provide physicians a better diagnostic tool, says Patterson.

The ultimate PET/CT frontier may be the brain. “PET/CT provides exquisite neurological images with an astonishing amount of information,” states Divgi. Yet, neurological PET/CT has not seen the exponential growth that oncologic imaging has. The barrier in this case is the lack of therapeutic options for neurological diseases like Parkinson’s and Alzheimer’s. Without therapeutic interventions, the utility of PET/CT or any diagnostic imaging tool is diminished, says Divgi.

Expert advice

Sites aiming to begin or expand their PET/CT program should invest wisely. An array of options exists. Insiders offer some pointers to help sites wade through:

  • A 16-slice CT component suffices for most applications including cardiac PET scanning. A 64-slice CT is needed for CT angiography, and a 64-slice PET/CT scanner may be in order for sites that need flexible coverage for radiation therapy planning. 4D PET/CT imaging nearly erases motion, says Blodgett, which could be useful if the scanner will be used for certain types of radiation therapy planning. UPMC plans to direct all potential PET/CT radiation therapy patients to a new 64-slice GE Discovery PET/CT scanner.
  • Sites eyeing the cardiac PET/CT market need to commit to an on-site generator for production of Rubidium-82. It’s difficult to reach an FDG PET/CT cardiac workload that supports the scanner; rubidium is needed for most cardiac studies.
  • Consider the patient population. Sites with a high load of obese patients or those considering radiation therapy PET/CT imaging should consider a wide-bore scanner.

PET/CT delivers

The latest round of data show that PET/CT lives up to its initial promise. That is, PET/CT does make a difference in oncology patient management, helping physicians more accurately detect the extent of disease and monitor response to therapy. It appears that the reimbursement climate could improve. Several clinical organizations have petitioned CMS for wider reimbursement based on the NOPR data. Other critical enablers fall on radiology’s shoulders. PET/CT providers need to educate clinicians, particularly oncologists, about the value of PET/CT and produce clinically relevant reports. PET/CT also plays an important role in cardiovascular imaging, filling gaps left by other modalities and saving time and money when used in ED situations. Finally, future developments, such as new tracers and therapeutic options for neurodegenerative diseases, could boost PET/CT applications in the next five to 10 years.