Health technology reviews

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Positron emission tomography (PET) scans for lymphoma

Status: Decision complete

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Positron emission tomography (PET) is a type of nuclear medicine imaging that utilizes small amounts of radioactive materials called radiotracers to examine and measure physiological functions in the body. The more energy a group of cells needs, the more the radiotracer will build up in that location, revealing a metabolic “hot spot” on three dimensional images reconstructed by a computer. For lymphoma, the radioactive particle most commonly used for PET is 18fluorine, which binds to glucose to form fluorodeoxy-D-glucose (FDG). Most types of lymphoma are metabolically active and use more glucose compared with normal structures (i.e. are termed FDG avid). This results in greater uptake of the radioactive FDG creating a “hot” spot on the PET image. In general, 18FDG-PET is not used for initial diagnosis of lymphoma or for routine surveillance following treatment completion. 18FDG-PET has become widely used as an imaging tool for staging of lymphoma after histological diagnosis and for interim evaluation (e.g. restaging and evaluation treatment response) although there is some debate regarding the value of interim PET based on the quality of evidence available and use of various criteria for PET interpretation in the literature. There are data indicating that 18FDG-PET may be a predictor of prognosis when performed early during treatment. Recently, studies have emerged which explore the role of PET findings for adapting therapy.

Today, most PET scans are performed on combination PET and CT scanners. The combined PET/CT scans provide images that pinpoint the anatomic location of abnormal metabolic activity within the body and have been shown to provide more accurate diagnoses than the two scans performed separately. Most clinical guidelines recommend the use of PET in conjunction with diagnostic CT, whether each test is done separately or via an integrated PET/CT scanner for initial staging and re-staging at critical points after treatment.

Policy context

This topic was originally reviewed in 2011. It is being re-reviewed in 2018 based on newly available, published evidence.

Primary criteria ranking

  • Safety = Medium
  • Efficacy = High
  • Cost = Medium

Assessment timeline

  • Draft key questions published: June 14, 2018
  • Public comment period: June 15, to 28, 2018
  • Final key questions published: July 12, 2018
  • Draft report published: August 31, 2018
  • Public comment period: August 31, to October 1, 2018
  • Final report published: October 18, 2018
  • HTCC public meeting: November 16, 2018