Archived Policies - Radiology


Positron Emission Tomography (PET)

Number:RAD605.001

Effective Date:02-01-2005

End Date:02-29-2008

Coverage:

EPILEPTIC SEIZURES:

Positron Emission Tomography (PET) is considered medically necessary for the assessment of selected patients with epileptic seizures who are candidates for surgery.

NOTE:  Appropriate candidates are those patients who have complex partial seizures that have failed to respond to medical therapy and who have been advised to have a resection of a suspected epileptogenic focus located in a region of the brain accessible to surgery.  Conventional techniques for seizure localization must have been tried and provided data that suggested a seizure focus, but were not sufficiently conclusive to permit surgery.

EEG's AND PET EXAMINATION: The purpose of the PET examination should be to avoid subjecting the patient to extended pre-operative electroencephalographic recording with implanted electrodes.

ALZHEIMER’S DISEASE/DEMENTIA:

Positron Emission Tomography (PET) is considered experimental, investigational, and unproven as a diagnostic tool for suspected Alzheimer’s disease/Dementia.

ONCOLOGIC APPLICATIONS:

The current status of PET scanning for various oncologic indications is provided in the following grid:

Clinical Condition

Diagnosis or Detection

Disease Staging or Restaging

Treatment Response Monitoring

Melanoma

Investigational

Medically necessary to assess extranodal spread of malignant melanoma at initial staging or restaging.

Investigational to detect regional lymph node metastases in clinically localized melanoma scheduled for sentinel node biopsy.

Investigational

Lymphoma, including Hodgkin's disease

Investigational

Medically necessary for initial staging or restaging in known lymphoma.

Investigational

Lung Cancer

Medically necessary when evaluation of a solitary pulmonary nodule by CT scan and chest x-ray is inconclusive.

Medically necessary for initial staging or restaging in known lung cancer.

Investigational

Colorectal Cancer

Investigational

Medically necessary to detect and assess resectability of hepatic or extrahepatic metastases of colorectal cancer.

Investigational

Pancreatic

Investigational

Investigational

Investigational

Head and Neck Cancer

Medically necessary to identify an unknown primary suspected to be head and neck cancer.

Medically necessary to stage the cervical lymph nodes for patients with established head and neck cancer and assess the resectability of the tumor.

Medically necessary to detect residual or recurrent disease following treatment.

Esophageal Cancer

Investigational

Medically necessary for initial staging and restaging.

Investigational

Breast Cancer

Investigational

Medically necessary when used to investigate patients with established breast cancer who have signs, symptoms or lesions AND that standard imaging, including nuclear, CT and MRI scans has been unable to reveal the cause.

Investigational

Ovarian Cancer

Investigational

Investigational

Investigational

Thyroid Cancer

Investigational

Investigational

Investigational

Other Oncologic Applications

Investigational

Investigational

Investigational

Unknown Primary

Medically necessary for unknown primary when ALL of the following are met:

Single site disease outside the cervical lymph nodes;

Local or regional treatment for single site metastatic disease is being considered;

Workup for occult primary tumor was negative;

PET scan will be used to rule out or detect additional sites of disease that would eliminate the rationale for local or regional treatment.

Investigational for evaluation of unknown primary including but not limited to the following:

As part of the initial workup of an unknown primary;

As part of the workup of patients with multiple sites of disease.

CARDIAC APPLICATIONS

In terms of cardiac applications, PET scanning has focused on the following 2 distinct clinical situations:

MYOCARDIAL PERFUSION

Cardiac PET scanning is considered medically necessary as a technique of identifying myocardial perfusion defects and thus diagnose CAD.

NOTE:  In terms of myocardial perfusion studies, patient selection criteria or PET scans involve an individual assessment of the pretest probability of coronary artery disease (CAD), based both on patient symptoms and risk factors.  Patients at low risk for CAD may be adequately evaluated with exercise electrocardiography.  Patients at high risk for CAD may not benefit from a non-invasive assessment of myocardial perfusion, since, in this setting, a negative test may represent a false negative result.  These patients may be immediately referred to coronary angiography.

MYOCARDIAL VIABILITY

Cardiac PET scanning is considered medically necessary to assess the myocardial viability in patients with severe left ventricular dysfunction as a technique to determine candidacy for a revascularization procedure.

NOTE:  Patient selection criteria for PET scans for myocardial viability are typically those patients with severe left ventricular dysfunction who are under consideration for a revascularization procedure.  A PET scan may determine whether the left ventricular dysfunction is related to viable on nonviable myocardium.  Patients with viable myocardium may benefit from revascularization, while those with non-viable myocardium will not.  As an example, PET scans are commonly performed in potential heart transplant candidates to rule out the presence of viable myocardium. 

OTHER APPLICATIONS

The use of PET for all other indications is considered experimental, investigational and unproven.

PET/CT FUSION IMAGING

PET/CT Fusion imaging may be considered medically necessary when used for the indications listed in this policy that are considered eligible for PET imaging alone.

PET/CT Fusion imaging is considered experimental, investigational, and unproven when used for indications that under this policy are considered to be ineligible for PET imaging alone.

Description:

PET scans are based on the use of positron emitting radionuclide tracers coupled to organic molecules, such as glucose, ammonia, or water.  The radionuclide tracers simultaneously emit 2 high-energy photons in opposite directions that can be simultaneously detected (referred to as coincidence detection) by a PET scanner, consisting of multiple stationary detectors that encircle the area of interest. 

A variety of tracers are used for PET scanning, including oxygen-15, nitrogen-13, carbon-11, and fluorine-18.  Because of their short half-life, tracers must be made locally, the majority requiring an on-site cyclotron.

This policy only addresses the use of radiotracers detected with the use of dedicated PET scanners.  There is a similar procedure to PET that may be referred to as FDG-SPECT, metabolic SPECT, or PET using a gamma camera.  In this procedure radiotracers such as FDG may be detected using SPECT cameras.

PET/CT FUSION IMAGING

PET/CT Fusion Imaging is a new diagnostic tool for the staging and restaging of cancer.  Patients can be examined with both CT and PET in a single examination.  This new technology correlates 2 simultaneous imaging modalities for a comprehensive examination that combines anatomic data with functional or metabolic information.   The CT images are used for anatomic reference of the tracer uptake patterns images in PET, as well as for attenuation correction of the PET data.

Rationale:

EPILEPTIC SEIZURES:

Conventional techniques for seizure localization may provide data that suggest a seizure focus.  However, the data may not be conclusive to permit surgery.  The purpose of the PET examination should be to avoid subjecting the patient to extended pre-operative electroencephalographic recording with implanted electrodes.

ONCOLOGIC APPLICATIONS:

Lung Cancer:  PET scanning may have a clinical role in patients with solitary pulmonary lung nodules in whom the diagnosis is uncertain after prior CT scan and chest x-ray.  In patients with known lung cancer, the clinical value of PET scanning relates to improved staging information regarding the involvement of mediastinal lymph nodes, which generally excludes patients from surgical excision.

Melanoma:  Surgical resection for melanoma is limited to those with local disease.  Patients with widespread disease are not candidates for resection.  PET scanning has been investigated as both a technique to detect widespread disease as part of an initial staging procedure and also to evaluate the status of the local lymph nodes to determine the necessity of sentinel node biopsy.  To consider PET a useful alternative to sentinel node biopsy, it must have high sensitivity and specificity when either sentinel node biopsy or lymph node dissection serves as the reference standard. A 1999 TEC Assessment concluded that PET is not as beneficial as sentinel node biopsy in assessing regional lymph nodes.

Lymphoma (including Hodgkin`s disease): A 1999 TEC Assessment concluded that when PET is added to conventional imaging, it can provide useful information for selective effective treatment that is appropriate to the correct stage of disease.  

Colorectal Cancer:  A 1999 TEC Assessment concluded that PET scanning adds useful information to conventional imaging in detecting hepatic and extrahepatic metastases.  In particular, PET can detect additional metastases leading to more identification of non-resectable disease, allowing patients to avoid surgery.  In regard to using PET as a technique to evaluate the presence of postoperative scar vs. recurrent disease the key concern is whether the negative predictive value for PET is sufficiently high to influence decision making, specifically to avoid tissue biopsy when the PET scan is negative.  The available studies suggest a probability of false negative results of 8%, making it unlikely that patients and physicians would be willing to forgo histologic sampling and delay potentially curative repeat resection.

Pancreatic Cancer:  A 1999 TEC Assessment concluded that the level of diagnostic performance of PET to distinguish between benign or malignant pancreatic masses or as a staging technique for pancreatic cancer is not adequate enough to recommend against biopsy.

Head and Neck Cancer:  A 2000 TEC Assessment concluded that when compared with other imaging modalities, the pooled data from a variety of studies suggested that PET had a better diagnostic performance compared to CT and MRI for the covered indications.

Esophageal Cancer:  2002 TEC Assessment states evidence is lacking on PET`s use to differentiate between esophageal cancer and benign conditions.  Regarding evaluation of treatment response, only 1 small study was identified.  While PET found evidence of response not shown on CT, these data are insufficient to permit conclusions regarding the value of PET in evaluation response to treatment. 

Ovarian Cancer:  For primary evaluation the ability to rule out malignancy with a high negative predictive value would change management by avoiding unnecessary exploratory surgery.  However, available studies suggest that PET scanning has poorer negative predictive value compared to other options, including transvaginal ultrasound, doppler studies, or MRI.  Adding PET scanning to transvaginal ultrasound (TRUS) or MRI did not improve results.  Positive predictive value is of greatest importance in evaluating patient with known ovarian cancer, either to detect disease recurrence or progression or monitor response to treatment.  There was insufficient evidence to permit scientific conclusions regarding this application. 

Breast Cancer:  A 2001 TEC Assessment focused on multiple applications of PET scanning in breast cancer, including characterization of breast lesions, staging axillary lymph nodes, detection of recurrence, and evaluating response to treatment.  Most of the data regarding PET scanning for breast cancer focuses on its use as a technique to further characterize breast lesions such that patients could avoid biopsy of a mammographically indeterminate or low suspicion lesion.  The key statistic in this analysis is the false negative rate, which may range from 5.5% to 8.5%.  Given the ease of breast biopsy, this false negative rate may be considered unacceptable, and thus patients may undergo biopsy regardless of the results of a PET scan.  For most all other applications there was inadequate data regarding how the use of PET scans may be used to benefit health outcomes, primarily due to the lack of data regarding diagnostic performance in the different settings.  

NOTE:  HCSC is aware of Medicare's recent coverage determination regarding PET imaging of breast cancer and after review have determined to follow our outlined position as stated in the coverage section of this policy (see grid regarding oncologic applications of PET).

Unknown Primary:  The 2002 TEC Assessment concluded that the TEC criteria were met for the limited indication of the work up and management of patients with unknown primaries and a single site of metastatic disease.  Specifically, local or regional therapy may be offered to these patients.  In this setting PET scanning may be used to verify the absence of disseminated disease.  The use of PET can contribute to optimal decision-making regarding the appropriateness of local or regional therapy.

Thyroid Cancer:  Information from a 2004 Medline review consisted of review articles, case studies, and small clinical studies.    One report stated that Nuclear medicine has a role mainly in differentiated thyroid cancer (DTC) which is the majority of thyroid cancers and stated further there is no role in staging.  Several studies in this report documented the higher accuracy of PET, when compared with other imaging modalities in the evaluation of patients with recurrent metastatic DTC.  One clinical blinded study (26 patients) showed CT superior to PET for Medullary Thyroid Carcinoma (MTC).

Although review articles and some small clinical studies reported a sensitivity ranging from 60 to 90%, more long term outcome studies are necessary to determine if the diagnostic value of PET imaging for thyroid cancer results in a change in treatment management.  

CARDIAC APPLICATIONS:

MYOCARDIAL PERFUSION

In patients with symptoms suggestive of CAD, a central clinical issue is to determine whether a coronary angiogram is necessary for further work-up.  A variety of non-invasive imaging tests, including PET (using rubidium-82) and SPECT scans, have been investigated as a means of identifying reversible perfusion defects, which may reflect coronary artery disease, and thus identify patients who may benefit from further work-up with an angiogram.  The ACC/AHA guidelines on radionuclide imaging note that compared to SPECT scans, PET scans have demonstrated statistically significantly higher diagnostic accuracy for detecting angiographically documented CAD.  However, the guidelines describe technical difficulties and referral biases that may have negatively impacted the diagnostic accuracy of SPECT scans.  The guidelines further state: "PET is an expensive imaging modality, and whether the greater cost of PET is justified by a possible improvement in diagnostic accuracy requires further rigorous study.  Thus, until data from large-scale, definitive studies are published, PET is considered an effective modality for the noninvasive diagnosis of CAD."

MYOCARDIAL VIABILITY

PET has perhaps been most thoroughly researched as a technique to assess myocardial viability to determine candidacy for a coronary revascularization procedure.  For example, a patient with a severe stenosis identified by coronary angiography may not benefit from revascularization if the surrounding myocardium is non-viable.  A fixed perfusion defect, as imaged on SPECT scanning or stress thallium echocardiography, may suggest non-viable myocardium.  However a PET scan may reveal metabolically active myocardium, suggesting areas of hibernating myocardium that would indeed benefit from revascularization.  The ultimate clinical validation of this diagnostic test is the percentage of patients who experience improvement in left ventricular dysfunction after revascularization of hibernating myocardium, as identified by PET scanning.   The American College of Cardiology (ACC) and the American Heart Association (AHA) have jointly published guidelines for the clinical use of cardiac radionuclide imaging, including PET scans.  The guidelines report that, overall, PET scanning for myocardial viability is associated with positive and negative predictive accuracies of 85% in identifying regions that are associated with clinical improvement after revascularization.

ALZHEIMERS DISEASE

Although the technology is evolving, larger studies are necessary before PET can be determined feasible for diagnosing Alzheimer’s. Early detection of dementia could be helpful if it led to improved patient management such as treatment through informed decision-making and use of medications to slow progression of the disease.  However, the evidence supporting these potential benefits is lacking and patients still face a potential risk of harm.     A report by the U.S. Preventive Service Task Force published in 6/2003 noted that no evidence was found that screening and early treatment makes an important difference in the lives of patients and their families.   

NOTE:  HCSC is aware of Medicare's recent coverage determination regarding PET imaging as a diagnostic tool for suspected Alzheimer’s disease/Dementia.  After review, HCSC has developed this coverage position of experimental, investigational and unproven as noted in the coverage section of this policy.

PET/CT FUSION IMAGING

The preliminary reports on the use of PET/CT fusion imaging are promising.  The data from these reports indicates that PET/CT provides accurate information about anatomic planes and excludes false-positive findings.  In addition, findings suggest accurate staging and improved evaluation of the response to therapy.

Contract:

Each benefit plan, summary plan description or contract defines which services are covered, which services are excluded, and which services are subject to dollar caps or other limitations, conditions or exclusions. Members and their providers have the responsibility for consulting the member's benefit plan, summary plan description or contract to determine if there are any exclusions or other benefit limitations applicable to this service or supply. If there is a discrepancy between a Medical Policy and a member's benefit plan, summary plan description or contract, the benefit plan, summary plan description or contract will govern.

Coding:

PET/CT Imaging:

As a general principle, payment for PET/CT Fusion imaging should be the same as for PET imaging alone.


Medicare Coverage:

Medicare and HCSC have different criteria for coverage depending on indication.  For specific coverage criteria for Medicare see their web site at www.cms.hhs.gov.

References:

BCBSA TEC Evaluations:

Positron Emission Tomography, July 1989, pages 155-183.

Positron Emission Tomography of the Heart, June 1991, pages 186-222.

Positron Emission Tomography (PET) of Central Nervous System Diseases, April 1992, pages 32-110.

Positron Emission Tomography for Assessment of Myocardial Viability, Volume 9, No.29, October 1994, pages 1-19.

Positron Emission Tomography for the Diagnosis of Cardiomyopathy, Volume 9, No. 30, October 1994, pages 1-10.

FDG Positron Emission Tomography for Non-CNS Cancer, Volume 10, No. 20, October 1995, pages 1-33.

PET Myocardial Perfusion Imaging for the Detection of Coronary Artery Disease - Clinical Assessment, Volume 10, No. 21, October 1995, pages 1-25.

PET, SPECT, or MRS in the Differential Diagnosis of Dementias, Volume 10, No. 29, April 1996, pages 1-15.

PET or SPECT in the Management of Seizure Disorders, Volume 11, No. 33, March 1997, pages 1-17.

PET or SPECT in the Diagnosis and Management of Brain Tumors, Volume 11, No. 34, March 1997, pages 1-25.

PET or SPECT for the Assessment of Cerebrovascular Disease, Volume 11, No. 35, March 1997, pages 1-29.

FDG Positron Emission Tomography for Non-CNS Cancers, Volume 12, No. 3, May 1997, pages 1-63.

PET Myocardial Perfusion Imaging for the Detection of Coronary Artery Disease - Cost Effectiveness Analysis, Special Assessment, 1998, pages 1-18.

FDG Positron Emission Tomography In Colorectal CA, Volume 14, No. 25, 4/2000.

FDG Positron Emission Tomography In Lymphoma, Volume 14, No. 26, 4/2000.

FDG Positron Emission Tomography In Melanoma, Volume 14, No. 27, 4/2000.

FDG Positron Emission Tomography In Pancreatic Cancer, Volume 14, No. 28.

FDG Positron Emission Tomography In Head and Neck Cancer, Volume 15, No. 4, 6/2000.

FDG Positron Emission Tomography for Evaluating Breast Cancer, Volume 16, No. 5, 8/2001

FDG Positron Emission Tomography for Evaluating Esophageal Cancer, Volume 16, No. 21, 4/2002

FDG Positron Emission Tomography (PET) For the Detection of Ovarian Cancer. 6/2002

FDG Positron Emission Tomography to Manage Patients with an Occult Primary Carcinoma and Metastasis Outside the Cervical Lymph Nodes, 6/2002.

FDA Internet Bulletin Board (on-line), 02/98, The History and Evolution of PET, How PET Works, The Cyclotron and PET, Selected PET Resources on the Internet. www.fda.gov

Gourgiotis L., Sarlis L., et al.  Localization of medullary thyroid carcinoma metastasis in a multiple endocrine neoplasia type 2A patient by 6-[18F]-fluorodopamine positron emission tomography.  J Clin Endocrinol Metab.  (2003 February) 88(2): 637-41

Cripps F., Gerali A.et al.  FDG-PET in thyroid cancer.  Tumori (2003 September/October) 89(5): 540-3.

Boer A., Szakall S. Jr., et al.  FDG PET imaging in hereditary thyroid cancer.  European Journal of Surgical Oncology.  (2003 December) 29(10): 922-28.

Khan N., Oriuchi N., et al.  PET in the follow-up of differentiated thyroid cancer.  British Journal of Radiology (2003) 76, 690-95.

Marchesi M., Biffoni M., et al.  False-positive finding on 18F-FDG PET after chemotherapy for primary diffuse large B-cell lymphoma of the thyroid: a case report.  Japan Journal of Clinical Oncology (2004 May) 34(5): 280-1.

Gotthardt m, Battmann A, et al.  18F-FDG PET, somatostatin receptor scintigraphy, and CT in metastatic medullary thyroid cardinoma: a clinical study and an analysis of the literature.  Nucl Med Commun (2004 May) 25(5): 439-43.

Mansi L, Moncayo R, et al.  Nuclear medicine in diagnosis, staging and follow-up of thyroid cancer.  Q J Nucl Med Mol Imaging (2004 June) 48(2): 82-95.

Beyer, T, Gerald A.M., et al, Acquisition Protocol Considerations for Combined PET/CT Imaging, The Journal of Nuclear Medicine, (January 2004) 45(1): (Supplement).

Screening for Dementia:  Recommendation and Rationale, American Family Physician.  U.S. Preventive services Task Force: (March 15 2004).

Patwardhan M.B., McCrory D.C., et al. Alzheimer disease: operating characteristics of PET—a meta-analysis. Radiology (2004 April) 231(1):73-80.

Verchakelen J., De Wever W., et al. Role of Computed Tomography in Lung Cancer Staging, Current Opinion Pulmonary Medicine. (2004) 10(4):248-255.

Policy History:

Archived Document(s):

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