Journal of nuclear medicine : official publication, Society of Nuclear Medicine
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In the Western world, more than 90% of head and neck cancers are head and neck squamous cell carcinomas (HNSCCs). The most appropriate treatment approach for HNSCC varies with the disease stage and disease site in the head and neck. Concurrent chemoradiotherapy has become a widely used means for the definitive treatment of locoregionally advanced HNSCC. ⋯ Hypoxia is a common phenomenon in HNSCC and renders cancers resistant to chemo- and radiotherapy. Imaging and quantification of hypoxia with PET probes is under study and may become a prerequisite for overcoming chemo- and radioresistance using radiosensitizing drugs or hypoxia-directed irradiation techniques and for monitoring the response to these techniques in selected groups of patients. Although (18)F-FDG PET/CT will remain the major clinical tool for monitoring treatment in HNSCC, other PET probes may have a role in identifying patients who are likely to benefit from treatment strategies that include biologic agents such as epidermal growth factor receptor inhibitors or VEGF inhibitors.
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Most anticancer drugs are effective only in subgroups of patients, and our current understanding of tumor biology does not allow us to predict accurately which patient will benefit from a specific therapeutic regimen. Various techniques have, therefore, been developed for monitoring tumor response to therapy, but measuring tumor shrinkage on CT represents the current standard. Although response assessment on CT has been refined over many years, fundamental limitations remain. ⋯ In a variety of solid tumors, single-center studies have indicated that (18)F-FDG PET may provide earlier or more accurate assessment of tumor response than CT, suggesting that (18)F-FDG PET could play a significant role in personalizing the treatment of malignant tumors. However, generally accepted criteria for response assessment in solid tumors are missing, which makes it frequently impossible to compare the results of different studies. International guidelines and criteria for response assessment by (18)F-FDG PET in solid tumors are, therefore, eagerly awaited.
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The purpose of this article is to review the status and limitations of anatomic tumor response metrics including the World Health Organization (WHO) criteria, the Response Evaluation Criteria in Solid Tumors (RECIST), and RECIST 1.1. This article also reviews qualitative and quantitative approaches to metabolic tumor response assessment with (18)F-FDG PET and proposes a draft framework for PET Response Criteria in Solid Tumors (PERCIST), version 1.0. ⋯ Anatomic imaging alone using standard WHO, RECIST, and RECIST 1.1 criteria have limitations, particularly in assessing the activity of newer cancer therapies that stabilize disease, whereas (18)F-FDG PET appears particularly valuable in such cases. The proposed PERCIST 1.0 criteria should serve as a starting point for use in clinical trials and in structured quantitative clinical reporting. Undoubtedly, subsequent revisions and enhancements will be required as validation studies are undertaken in varying diseases and treatments.
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In patients with locally advanced esophageal cancer, preoperative chemotherapy or chemoradiotherapy has been shown to improve outcome with respect to survival. Patients who respond to induction therapy have a significantly improved survival, compared with patients who do not respond to the therapy. However, surrogate markers that predict response or prognosis-especially early in the course of therapy-are not available in clinical routine. ⋯ From a methodologic point of view, the most important issue in therapy monitoring using (18)F-FDG PET and PET/CT is the standardization of patient preparation, data acquisition and processing, and data interpretation, especially for prospective randomized multicenter studies. In conclusion, single-center studies investigating response assessment in patients with esophageal cancer have provided promising results. In the future, prospective randomized multicenter trials will have to be performed and research will address new imaging probes and innovative therapy regimens.
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PET with (18)F-FDG is a standard staging procedure for most lymphoma subtypes. Performed during and after therapy for Hodgkin lymphoma (HL) and aggressive non-Hodgkin lymphoma (NHL), (18)F-FDG PET results have a high prognostic value and correlate with survival. (18)F-FDG PET has been incorporated into revised response criteria for aggressive lymphomas, and several ongoing trials are under way to investigate the value of treatment adaptation based on early (18)F-FDG PET results for HL and aggressive NHL. ⋯ So that trial results can be compared and translated easily into clinical practice, uniform and evidence-based guidelines for the interpretation and reporting of response monitoring scans are warranted. Because it is still not proven that the use of interim (18)F-FDG PET can improve patient outcomes, we recommend examination of the use of (18)F-FDG PET for response monitoring in appropriately designed clinical trials.