Special Report: Positron Emission Tomography for the Indication of Post-Treatment Surveillance of Cancer
Executive Summary
Background
The use of positron emission tomography (PET) and the related procedure, PET with computed tomography (PET/CT), is increasing rapidly in the U.S. In this Special Report, the term “PET” will be used generally to describe PET or PET/CT. The most common use of PET scanning is for the diagnosis and staging of several types of cancer.
However, PET is also commonly used after initiation and completion of treatment for cancer. One such potential use is surveillance, defined for the purposes of this Special Report as use of PET beyond the completion of treatment, in the absence of signs or symptoms of cancer recurrence or progression, for the purpose of detecting recurrence or progression or predicting outcome. Surveillance PET might be performed at some regular interval after completion of treatment. The duration of time beyond completion of treatment for a PET scan in order to be considered a surveillance PET is not defined with certainty, but the criterion exists in order to differentiate a surveillance PET scan from a PET scan done at a time close to or at the end of chemotherapeutic treatment as a method of determining whether disease has responded to treatment, assessing residual disease, or predicting prognosis.
Uses of PET after initiation or completion of treatment that are not under consideration in this Report include 1) PET during treatment in order to alter therapy or predict prognosis; 2) PET shortly after treatment or a treatment cycle in order to alter therapy or predict prognosis; 3) PET for the detection of recurrence in patients with signs, symptoms, or other positive imaging test(s); and 4) PET for determining the extent of cancer in a patient with confirmed recurrence or progression (restaging). The terminology for describing indications for PET is, unfortunately, not standard or consistent. In the review of studies and systematic reviews done in support of this Report, the terms “restaging” or “surveillance” were often used to describe PET scans performed for any of the above-listed indications, as well as for the particular definition of surveillance in this Report.
Objective
The purpose of this Special Report is to present and discuss several issues relevant to the use of PET scanning for post-treatment surveillance in the context of cancer therapy. Principles of surveillance after treatment for cancer will be discussed. Other uses of PET scanning after initiation of treatment will be described. Guidelines and evidence regarding the use of PET for surveillance will be discussed.
Search Strategy
The MEDLINE® database was searched (via PubMed) in different ways, as follows:
- text words: (pet or positron) AND (cancer OR oncology) AND (surveillance OR follow-up);
- Medical Subject Heading® (MeSH) terms: Tomography, Emission-Computed AND Neoplasms.
The search was limited to articles written in English and involving human subjects but was not limited by publication date. Systematic reviews and technology assessments, meta-analyses and specialty society guidelines in oncology were reviewed for specific findings and/or recommendations. This search was last updated in May 2010. In addition, reference lists of key articles were searched for additional citations.
Selection Criteria
Because of the lack of outcome studies for surveillance PET in oncology, selection and data extraction focused on systematic reviews/technology assessments of the use of PET in oncology, relevant guideline statements, and anecdotal studies and convenience samples to illustrate how PET might be applied in the surveillance setting.
Main Results
There is simply inadequate direct and indirect evidence supporting the efficacy of PET scanning for the purpose of surveillance. Reflecting this lack of evidence, current practice guidelines appear unanimously to recommend against the use of PET for surveillance. No strong support of the use of PET for surveillance was found in editorials, case reports, or other studies.
Author’s Conclusions and Comments
Given such problems such as lead time bias, length bias, and the uncertain diagnostic characteristics of PET in the surveillance setting, it would be difficult to determine whether the efficacy of PET for surveillance could be determined with observational data. Clinical trials may be necessary to determine whether PET surveillance is effective in improving health outcomes.
*This Special Report evaluates the use of positron emission tomography as a method of post-treatment surveillance in oncology. It does not attempt to address whether the TEC Criteria are met.
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ASCO; breast cancer; cervical cancer; colorectal cancer; CT; FDG; follow-up; incidental findings; MRI; NCCN; PET; positron emission tomography; radiation exposure; solid tumors; surveillance;
