PET scanner update

Patient undergoing a PET scan of the brain.

Photo courtesy of Dr. E. Tanaka.

The positron emission tomography (PET) scanner is a nuclear medicine imaging technology that allows detailed diagnostic measurement of physiological and biochemical bodily processes. This technology can be used to detect and evaluate different types of cancer; or to examine brain function, blood flow or heart disease.

How it works

During a PET scan, a tiny dose of positron-emitting radiopharmaceutical (PER) is administered intravenously before the patient reclines inside a large, doughnut-shaped machine.

When the radioactive tracer travels through the body, radioactive particles decay and release positrons, which then pair up with electrons and subsequently emit photons.

Positron-emitting radiopharmaceutical (PER) tracers

One of the most widely used tracers is ¹⁸F-FDG, a radioactive glucose analogue. After injection into a patient's blood stream, FDG is taken up by the cancer cells at a more rapid rate than normal cells and this allows cancers to be seen as “hot spots” on the PET scan.

PER tracers are produced in a laboratory from radioisotopes generated by a particle accelerator (cyclotron). As most PERs have a short shelf life, ranging from minutes to a few hours, radioisotopes must be produced close to the centres with PET scanners. This may limit patients’ access in some parts of Canada.

PER regulations

PER tracers have not yet been approved for use in Canada. Health Canada requires each site preparing PER tracers to obtain a Clinical Trial Application. In addition, recorded data must be submitted for all patients receiving the tracers.

Location of PET Scanners

Table 1 outlines PET scanner distribution in the five provinces that have adopted the technology, including installations planned for 2005.

Table 1: Location of publicly funded PET scanners and cyclotrons in Canada*

* Data supplied by Henri Vienneau, executive director of the Nuclear Medicine Alliance.

^† Includes PET scanners used for patient care (through clinical trials) and scanners used for research purposes only.

Evidence of clinical effectiveness

A large number of primary research studies and systematic reviews have examined the potential benefit of PET scans to manage various cancers.

A rapid review in 2004 by the UK National Health Service, Health Technology Programme, found that there was evidence to support the use of PET scans in the staging of non-small cell lung cancer; the evaluation of recurrent colorectal cancer; and the restaging of Hodgkin’s lymphoma after induction therapy. There was also sufficient evidence to support the use of PET scans to diagnose solitary pulmonary nodules and occult tumours in the head and neck; and to detect metastases in breast cancer and thyroid cancer recurrence. The report concluded that the use of PET scans for other cancer management decisions requires further studies.[1] A further assessment and update of this review is in progress.

A 2003 Norwegian review (English summary published by the International Network of Agencies of Health Technology Assessment (INAHTA)) reported similar conclusions.[2]

Use in other countries

The clinical use of PET scans is routine in the US, many European countries and Japan. In the US, Medicare pays for PET scans for the diagnosis of most cancers, providing that data are submitted to a national PET data registry.[3]

Are PET scans cost-effective?

PET scans may save money in the short term through the elimination of other diagnostic and treatment procedures, such as unnecessary surgery.

There are, however, insufficient short-term cost-benefit analyses to draw conclusions and there are no long-term patient outcome studies.

AETMIS, the Quebec health technology assessment agency, developed an economic model to assess the cost-effectiveness of PET scans in non-small cell lung cancer. The cost was deemed to be acceptable for the corresponding life-year gained, but the AETMIS report concluded that the main advantages of PET scans were the improvement in quality of life; the reduction in useless debilitating interventions; and faster access to effective therapy.[4]

ICES, an Ontario-based health research agency, performed a systematic review on the cost-effectiveness of PET in 2001, with subsequent updates to 2004. There were a few non-Canadian studies available for the ICES review, most of low quality. The report concluded that PET is likely to be cost-effective for patients with some cancers and intractable seizures.[5]

Provincial funding for PET scan operation

Quebec provides funding for 1,500 scans annually at each of its four hospitals with PET scanners. Quebec is the only province with a billing code for physician interpretation of the scan.
Source: Henri Vienneau, executive director of the Nuclear Medicine Alliance, Montreal.

Ontario is providing funding for approximately 1,500 PET scans per year (over a two-year period) for patients enrolled in five clinical trials and a registry at four geographical sites. Indications covered are non-small cell lung, head and neck, breast and colorectal cancers, as well as single pulmonary nodule and suspected recurrent germ cell, thyroid and colorectal cancer.
Source: Shirley Lee, Ontario Ministry of Health and Long-Term Care, Medical Advisory Secretariat, Toronto.

Nova Scotia plans to purchase a PET scanner in 2005 and have a program operating by 2007. Specific operational funding has not been announced. While PERs may be shipped in initially, a cyclotron will be built to support the program.
Source: Valerie Bellefontaine, Nova Scotia Department of Health, Halifax.

Manitoba is funding up to 1,000 PET scans in the 2005 to 2006 fiscal year for the new PET/CT scanner at the Winnipeg Health Sciences Centre (first patient imaged July 7, 2005). Funding may increase to scan up to 2,000 patients a year thereafter, relative to clinical demand. It is planned that radioactive tracers will be manufactured in Edmonton and air-freighted to Winnipeg.
Source: Dr. Sandor Demeter, department of radiology, Health Sciences Centre, Winnipeg.

New Brunswick will provide $1.3 million to cover operational costs for two PET/CT scanners, expected to be operational by September 2006. PERs will be shipped in daily.
Source: Johanne Le Blanc, Health and Wellness, Fredericton.

Alberta funds clinical PET scans at the Cross Cancer Institute in Edmonton, from the global regional health budget.
Source: Dr. Sandy McEwan, Cross Cancer Institute, Edmonton.

British Columbia will fund 1,500 PET scans at the BC Cancer Agency’s Vancouver clinic during the 2005 to 2006 fiscal year. The new PET/CT scanner began operating in June 2005.
Source: Dr. Don Wilson, BC Cancer Agency, Vancouver.

References

[1] Facey K, et al. Positron emission tomography (PET) imaging in cancer management [Ultra Rapid Review]. Southampton (UK):2004.

[2] Morland B. Positron emission tomography (PET) - diagnostic and clinical use [INAHTA brief issue 2004/80]. Oslo: Norwegian Centre for Health Technology Assessment; 2004. Available: http://www.inahta.org/Reports.asp?name=Content11%2Fpublikationer%2F8%2F0480%5FSMM%5FPositron%5FEmission%5FTomography%5FDiagnostic%5FClinical%5FUse%2Epdf.

[3] Medicare launches efforts to improve care for cancer patients [news release]. Baltimore (MD): Centers for Medicare & Medicaid Services; 2005 Jan 28. Available: http://www.cms.hhs.gov/media/press/release.asp?Counter=1337

[4] Dussault FP, et al. Positron emission tomography in Quebec. Montreal (QC): Agence d'Evaluation des Technologies et des Modes d'Intervention en Sante; 2002. Available: http://www.aetmis.gouv.qc.ca/fr/publications/scientifiques/imagerie_medicale/2001_03_en.pdf.

[5] Institute for Clinical Evaluative Sciences. Health technology assessment of positron emission tomography (PET) in oncology - a systematic review. Toronto (ON): Institute for Clinical Evaluative Sciences; 2004. Available: http://www.ices.on.ca/webbuild/site/ices-internet-upload/file_collection/Pet%5Freport%5FApr%5F2004%5B1%5D%2Epdf.