Spence McCachren, MD

Lack of reimbursement kept PET imaging on a slow track for most of the 1990s. The PET community's efforts to churn out data to persuade the government of the modality's effectiveness began to pay off early in the new century.

In late 2000, federal officials recognized FDG-PET as a biologic modality and expanded coverage for six cancers to include diagnosis, staging, and restaging with PET. Although buoyed by this action, practitioners remain dissatisfied with the lengthy approval process required by the Centers for Medicare and Medicaid Services.

Nevertheless, PET and PET/CT procedures are becoming standard practice tools. The emphasis at many institutions is to ensure seamless integration of PET imaging within the hospital system. A team approach by oncologists, radiologists, nuclear medicine physicians, referring physicians, and administrators is critical for success at a PET center. The perspective of each member of the team must be taken into account.

PET imaging is best approached as a joint effort between the referring oncologist and the radiologist. This partnership may take time to forge, and it requires mutual education. Oncologists should feel confident that interpreting physicians will review all recent studies and correlate them with PET findings and that any discrepancies will prompt a call to the ordering physician.

Questions about disease in oncology practice usually involve a limited number of issues: What is it? Where is it? Is it changing? Is treatment effective? PET-and, increasingly, PET/CT-can assist with the answers: cancer versus benign, anatomic location, disease growth, early prediction of response, and early detection of relapse.

Referring physicians hope that PET will be less ambiguous and more sensitive than conventional imaging. PET is often complementary to conventional imaging, as the rapid acceptance of PET/CT has shown. It is no longer standard practice to review a PET scan side by side with a film CT scan; image fusion workstations or dedicated PET/CT scanners have become commonplace.

Referring physicians sometimes lack understanding of PET's strengths and shortcomings, leading to dissatisfaction with radiologists' interpretations and resulting in poor decision making. It takes time and experience to understand the situations that may give rise to false-positive and false-negative results. Physicians may display overconfidence in the accuracy of PET and in its positive and negative predictive value in particular scenarios. If the pretest probability of an abnormality is low, then the positive predictive value of an abnormal test is low, even if the test has relatively high sensitivity and specificity.

PET imaging is particularly important in assessing lung nodules, staging and restaging lung and colorectal cancers, and staging Hodgkin's disease and lymphomas. Restaging after therapy and identifying recurrence are also critical. PET may be the best imaging study to evaluate the spread of melanoma, and it shows great promise in breast, cervical, thyroid, and other cancers.

PET's analysis of treatment efficacy enables oncologists to change ineffective therapy early in the course of treatment. Additionally, improved staging with PET/CT results in fewer tests. Newer imaging agents, such as sodium fluoride, offer improved organ-specific imaging and may be useful in certain situations. PET may also have a role in cancer clinical trials.

Given a choice between PET and SPECT, an interpreting physician would always choose PET. PET can detect abnormalities smaller than 10 mm, whereas SPECT's range begins around 15 mm. Interpreting physicians clearly favor PET over anatomic-based imaging techniques such as CT. Although CT has higher spatial resolution and can detect abnormalities as small as 2 mm, PET has higher contrast resolution. Abnormalities are often more conspicuous because PET has very little background detail to distract the interpreting physician.

PET can detect cancer within a lymph node that is not enlarged on CT. It can find cancer in the liver and other organs that appear structurally normal on CT. This makes PET useful when CT fails to detect malignancy that is known to be present based on symptoms or blood tests.

The data provided by PET and CT are complementary, and their combination in one PET/CT procedure is rapidly gaining acceptance. Patients like the convenience of having both tests at one time, and interpreting physicians like the combination of molecular and anatomic data. The correlation of these two types of data is especially important when biopsy or surgery is being considered. PET/CT is also attractive to radiation oncologists, who must precisely define an area to be irradiated.

The referring physician and interpreting physician have an important relationship that requires close communication. The referring physician has to provide the clinical information that allows the interpreting physician to interpret rather than describe the findings seen on PET. The interpreting physician needs to educate the referring physician about when to order PET and how to use the results so that the most accurate diagnosis is achieved in the most cost-effective manner.

The interpreting physician must also be aware of the limitations of PET and educate referring physicians about them. PET may miss significant abnormalities if they are smaller than the resolution limits of the technique, which is currently about 5 to 10 mm. PET is problematic in patients with diabetes, who require more thorough preparation prior to the examination. Finally, some types of malignancy, such as prostate cancer, are not easily detected by PET using currently available radiopharmaceuticals.

PET may give false-positive results. Focal infections and other inflammatory lesions can have the same appearance as malignancy on a PET scan. False-positive and false-negative findings cannot be avoided, but communication between the referring physician and interpreting physician can minimize the incidence of these undesirable outcomes.

This year, nearly 1.4 million new cancer cases will be diagnosed. Only 54% of them will be approved for Medicare reimbursement, even though 77% of all cancers are diagnosed at age 55 and older. This situation highlights the need to focus on all payers, not just Medicare. Most of the major health plans have established some coverage guidelines for PET, and they don't all follow Medicare guidelines.

PET centers must identify their referring physician base and develop marketing and educational tools focused on the most appropriate clinical uses for PET, coupled with the covered clinical indications broken down by payer. PET providers should obtain a complete set of covered indications from each payer in their community and create a guide to be used by scheduling personnel. This guide can also be distributed to referring physician offices. If referring physicians do not have current coverage guidelines, they will often default to other imaging modalities.

In recent years, coverage, billing, and payment guidelines from the Centers for Medicare and Medicaid Services have become easier to understand. PET coverage by the CMS falls under a national coverage determination, which means that all carriers and fiscal intermediaries must provide coverage based on the national clinical guidelines. There are allowances for frequency guidelines, ICD-9 codes, and payments by the carriers, but almost all this information is published and easy to understand. Billing codes are consistent and policies are easy to interpret. For the first time, the CMS has agreed to participate in a PET registry project designed to provide additional information about the diagnostic accuracy and clinical utility of FDG-PET. The goal of the registry will be to collect patient management data that will guide expansion of coverage guidelines.

Private payers pose the greatest educational and operational challenges for PET providers. It is not unusual for a private payer to have two different sets of covered indications: one for its managed Medicare lives and one for the rest of its plans. It is important to remember that these are guidelines, and if administrators and interpreting and/or referring physicians take time to share evidence on PET's value for certain indications, carrier medical directors will often approve procedures on a case-by-case basis or even expanding coverage.

Many of the large private payers have contracted with "radiology benefit management organizations" such as MedSolutions and National Imaging Associates. These companies manage high-end/high-cost diagnostic imaging procedures by establishing utilization guidelines and preauthorization processes designed to direct patients to the most appropriate procedure, based on information from the referring physician. As these organizations expand, it will be very important for providers to understand how contracting is handled, networks are established, and new technology like PET/CT is identified for payment.

Hospital-based PET providers face a big challenge this year with the lower payment allowables established by the CMS. For most oncologic PET scans, the CMS based the calendar year 2005 payment on a 50-50 blend of the median cost and the 2004 new technology ambulatory payment classification rate. The payment allowable for the technical component dropped from $1450 in 2004 to $1150 in 2005. The FDG payment allowable decreased from $324 in 2004 to $211 in 2005.

Most nonhospital PET providers are seeing their payment allowables increase in 2005 by the 1.5% physician fee schedule conversion factor update. These payment allowables remain above $2000 for the technical component in most areas.

Six new PET and PET/CT CPT codes developed by the American Medical Association became effective Jan. 1. They are designed to differentiate a PET scan performed on a dedicated PET scanner from one done on a dual-modality PET/CT scanner.

We are seeing a rapid transition from dedicated PET scanners to combined PET/CT technology, which will bring PET into the radiology world much more rapidly. All those involved with PET imaging must work together. Sharing knowledge is the best way to ensure that PET imaging will be used to the best benefit of patients as well as to the hospital's bottom line.

Ms. Halliday is an independent consultant in Ovilla, TX. She was formerly associated with CTI. Dr. Segall is chief of nuclear medicine service at the VA Palo Alto (CA) Health Care System and an associate professor of radiology at Stanford University. Dr. McCachren is a hematologist-oncologist at Thompson Cancer Survival Center in Knoxville, TN.

Spence McCachren, MD

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All clinical sides take hard look at PET and PET/CT