Positron emission tomography in non-small-cell lung cancer: prediction of response to chemotherapy by quantitative assessment of glucose use.

PURPOSE: To prospectively evaluate the use of positron emission tomography with the glucose analog fluorodeoxyglucose (FDG-PET) to predict response to chemotherapy in patients with advanced non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with stage IIIB or IV NSCLC scheduled to undergo platinum-based chemotherapy were eligible for this study. Patients were studied by FDG-PET before and after the first cycle of therapy. Based on previous studies, a reduction of tumor FDG uptake by more than 20% as assessed by standardized uptake values (SUV) was used as a criterion for a metabolic response. Furthermore, changes in tumor SUVs were compared with changes in FDG net-influx constants (Ki) and tumor/muscle ratios (t/m). RESULTS: Fifty-seven patients were included in the study. There was a close correlation between metabolic response and best response to therapy according to Response Evaluation Criteria in Solid Tumors (P <.0001; sensitivity and specificity for prediction of best response, 95% and 74%, respectively). Median time to progression and overall survival were significantly longer for metabolic responders than for metabolic nonresponders (163 v 54 days and 252 days v 151 days, respectively). Similar results were obtained when Ki was used to assess tumor glucose use, whereas changes in t/m showed considerable overlap between responding and nonresponding tumors. CONCLUSION: In NSCLC, reduction of metabolic activity after one cycle of chemotherapy is closely correlated with final outcome of therapy. Using metabolic response as an end point may shorten the duration of phase II studies evaluating new cytotoxic drugs and may decrease the morbidity and costs of therapy in nonresponding patients.     

How heterogeneous is the cardiac autonomic innervation?

The rich autonomic innervation of the heart plays an important role in modifying cardiovascular function. Recently developed in vivo scintigraphic imaging techniques allow for visualization of the autonomic innervation of the heart. Studies using the modalities have shown heterogeneity of sympathetic innervation in various kinds of pathological conditions as well as normal human heart. The inferioposterior region shows typically less sympathetic innervation than the anterior region. In addition, neuropathic processes appear to commence in inferior-apical regions extending towards the base of the heart. Arrhythmogeneity has been related to the heterogeneous innervation of the heart and heterogeneous uptake of radiolabeled catecholamine analogues, such as I-123 metaiodobenzylguanidine, can be found in patients with arrhythmia. In dilated cardiomyopathy, reduced uptake indicates a poor prognosis which allows risk stratification for patients with heart failure. Heterogeneity of the reinnervation process following heart transplantation has also been investigated. Evidence was found of reinnervation primarily in the basal anterioseptal region and to a lesser degree in the inferioposterior and apical regions. Tracer approaches are uniquely suited to identify regionally altered innervation and provide tools for linking information on cardiac autonomic innervation with other clinical aspects. Received: 2 April 2001, Returned for revision: 28 June 2001, Revision received: 7 August 2001, Accepted: 31 August 2001