PET after completion of therapy should be performed at least 3 weeks, and preferably at 6 to 8 weeks, after chemotherapy or chemoimmunotherapy, and 8 to 12 weeks after radiation or chemoradiotherapy. Visual assessment alone is adequate for interpreting PET findings as positive or negative when assessing response after completion of therapy. Mediastinal blood pool activity is recommended as the reference background activity to define PET positivity for a residual mass > or = 2 cm in greatest transverse diameter, regardless of its location. A smaller residual mass or a normal sized lymph node (ie, < or = 1 x 1 cm in diameter) should be considered positive if its activity is above that of the surrounding background. Specific criteria for defining PET positivity in the liver, spleen, lung, and bone marrow are also proposed. Use of attenuation-corrected PET is strongly encouraged. Use of PET for treatment monitoring during a course of therapy should only be done in a clinical trial or as part of a prospective registry.

The rationale was to develop recommendations on the use of 18 F-FDG PET in breast, colorectal, esophageal, head and neck, lung, pancreatic, and thyroid cancer; lymphoma, melanoma, and sarcoma; and unknown primary tumor. Outcomes of interest included the use of 18 F-FDG PET for diagnosing, staging, and detecting the recurrence or progression of cancer. Methods: A search was performed to identify all published randomized controlled trials and systematic reviews in the literature. An additional search was performed to identify relevant unpublished systematic reviews. These publications comprised both retrospective and prospective studies of varied methodologic quality. The anticipated consequences of false-positive and false-negative tests when evaluating clinical usefulness, and the impact of 18 F-FDG PET on the management of cancer patients, were also reviewed. Results and Conclusion: 18 F-FDG PET should be used as an imaging tool additional to conventional radiologic methods such as CT or MRI; any positive finding that could lead to a clinically significant change in patient management should be confirmed by subsequent histopathologic examination because of the risk of false-positive results. 18 F-FDG PET should be used in the appropriate clinical setting for the diagnosis of head and neck, lung, or pancreatic cancer and for unknown primary tumor. PET is also indicated for staging of breast, colon, esophageal, head and neck, and lung cancer and of lymphoma and melanoma. In addition, 18 F-FDG PET should be used to detect recurrence of breast, colorectal, head and neck, or thyroid cancer and of lymphoma. PET is an imaging technique that provides unique information about the molecular and metabolic changes associated with disease. The technology has existed for more than 30 years but has been used clinically for only the last 10-15 years. In this period, dramatic improvements in technology, the routine availability of medical cyclotrons (to produce the necessary short-lived positron emitters), and favorable reimbursement decisions in the late 1990s have led to a tremendous increase in the use of this technology. The major area of clinical application is currently in oncology, with some application in cardiology and neurology.PET requires the use of molecules (radiopharmaceuticals) that are labeled with radioactive nuclides. The amounts of radiolabeled material administered are extremely small (10 26 -10 29 g) and have essentially no pharmacologic effect. In this regard, PET has the unique ability to assess molecular alterations associated with disease without perturbing or altering the fundamental underlying molecular and biochemical processes. Although the number of molecular probes that can be radiolabeled with positron emitters is extremely large, and clinical investigational uses number in the thousands, clinical practice has been limited principally to the use of a glucose analog labeled with the positron emitter 18 F-FDG. 18 F-FDG was first synthesized in 1978 (1) and has become the most commonly used radioph...

IMPORTANCE Amyloid positron emission tomography (PET) detects amyloid plaques in the brain, a core neuropathological feature of Alzheimer disease. OBJECTIVE To determine if amyloid PET is associated with subsequent changes in the management of patients with mild cognitive impairment (MCI) or dementia of uncertain etiology. DESIGN, SETTING, AND PARTICIPANTS The Imaging Dementia-Evidence for Amyloid Scanning (IDEAS) study was a single-group, multisite longitudinal study that assessed the association between amyloid PET and subsequent changes in clinical management for Medicare beneficiaries with MCI or dementia. Participants were required to meet published appropriate use criteria stating that etiology of cognitive impairment was unknown, Alzheimer disease was a diagnostic consideration, and knowledge of PET results was expected to change diagnosis and management. A total of 946 dementia specialists at 595 US sites enrolled 16 008 patients between February 2016 and September 2017. Patients were followed up through January 2018. Dementia specialists documented their diagnosis and management plan before PET and again 90 (±30) days after PET. EXPOSURES Participants underwent amyloid PET at 343 imaging centers. MAIN OUTCOMES AND MEASURES The primary end point was change in management between the pre-and post-PET visits, as assessed by a composite outcome that included Alzheimer disease drug therapy, other drug therapy, and counseling about safety and future planning. The study was powered to detect a 30% or greater change in the MCI and dementia groups. One of 2 secondary end points is reported: the proportion of changes in diagnosis (from Alzheimer disease to non-Alzheimer disease and vice versa) between pre-and post-PET visits. RESULTS Among 16 008 registered participants, 11 409 (71.3%) completed study procedures and were included in the analysis (median age, 75 years [interquartile range, 71-80]; 50.9% women; 60.5% with MCI). Amyloid PET results were positive in 3817 patients with MCI (55.3%) and 3154 patients with dementia (70.1%). The composite end point changed in 4159 of 6905 patients with MCI (60.2% [95% CI, 59.1%-61.4%]) and 2859 of 4504 patients with dementia (63.5% [95% CI, 62.1%-64.9%]), significantly exceeding the 30% threshold in each group (P < .001, 1-sided). The etiologic diagnosis changed from Alzheimer disease to non-Alzheimer disease in 2860 of 11 409 patients (25.1% [95% CI, 24.3%-25.9%]) and from non-Alzheimer disease to Alzheimer disease in 1201 of 11 409 (10.5% [95% CI, 10.0%-11.1%]). CONCLUSIONS AND RELEVANCE Among Medicare beneficiaries with MCI or dementia of uncertain etiology evaluated by dementia specialists, the use of amyloid PET was associated with changes in clinical management within 90 days. Further research is needed to determine whether amyloid PET is associated with improved clinical outcomes.

2-[ 18 F]Fluoro-2-deoxyglucose positron emission tomography (FDG-PET) assesses a fundamentalpropertyof neoplasia, theWarburgeffect.This molecularimaging technique offers acomplementary approach to anatomic imaging that is more sensitive and specific in certain cancers. FDG-PET has been widely applied in oncology primarily as a staging and restaging tool that can guide patient care. However, because it accurately detects recurrent or residual disease, FDG-PETalso has significant potential for assessing therapy response. In this regard, it canimprove patient management by identifying responders early, before tumor size is reduced; nonresponders could discontinue futile therapy. Moreover, a reductioninthe FDG-PETsignal withindays or weeks of initiating therapy (e.g., in lymphoma, non^small cell lung, and esophageal cancer) significantly correlates with prolonged survival and other clinical end points now usedin drug approvals.These findings suggest that FDGPETcould facilitate drug development as an early surrogate of clinicalbenefit.This article reviews the scientificbasis ofFDG-PETandits development andapplicationasavaluableoncologyimagingtool. Its potential to facilitate drug development in seven oncologic settings (lung, lymphoma, breast, prostate, sarcoma, colorectal, and ovary) is addressed. Recommendations include initial validation against approved therapies, retrospective analyses to define the magnitude of change indicative of response, further prospective validation as a surrogate of clinical benefit, and application as a phase II/III trial end point to accelerate evaluation and approval of novel regimens and therapies. FDG-PET (2-[18 F]Fluoro-2-deoxyglucose positron emission tomography) is an accepted and widely used clinical imaging tool in oncology. U.S. Medicare reimbursement of FDG-PET recently expanded to encompass all cancer patients participating in certain prospective studies or registries in addition to more general coverage in 10 defined oncologic settings. Primarily covered are disease diagnosis, staging, and restaging, but FDG-PET is also approved for monitoring response to therapy in locally advanced and metastatic breast cancers when a change in therapy is anticipated. Clinical trials in breast cancer and other settings [e.g., non -small cell lung cancer (NSCLC) and esophageal cancer] have shown that FDG-PET imaging can provide an early indication of therapeutic response that is well correlated with clinical outcome. FDG-PET thus has the potential to improve patient management, particularly by signaling the need for early therapeutic changes in nonresponders, thereby obviating the side effects and costs of ineffective treatment. As an early surrogate for clinical benefit, the modality also has the potential to facilitate oncologic drug development by shortening phase II trials and detecting clinical benefit earlier in phase III investigations. Studies to further explore and validate these approaches are needed and can be conducted in parallel with those employing end points now use...

The functional status of tumor ERs can be characterized in vivo by PET with FDG and FES. The results of PET are predictive of responsiveness to tamoxifen therapy in patients with advanced ER(+) breast cancer.