In the past 10 years, FDG-PET has become an important imaging modality in NSCLC. Its indication in the assessment of lung nodules and staging is based on large prospective experience, further supported by some meta-analyses. This evidence has important consequences for patient management, which recently was proved in a randomized trial that showed a reduction in the number of futile
thoracotomies by preoperative PET. The use of FDG-PET could become more widespread when commercial
isotope distributors are able to deliver FDG so that an on-site
cyclotron is no longer a prerequisite. FDG has a half-life of 110 minutes, so a practical distribution radius of 200 km should be feasible. Current indications for PET in the staging of newly diagnosed NSCLC are mainly the patients who are considered to be candidates for radical treatment. The technique does not have a clinical indication in other patients--for example, when metastatic lymph nodes are detected at clinical examination, when a simple ultrasound study already points to diffuse hepatic
metastases, or in cases of poor performance status. PET also has prognostic value; it can be used for the evaluation of response or restaging after
radiotherapy or
chemotherapy and for early detection of relapse. The combination of CT and PET improves
radiotherapy planning and it is to be expected that combined CT-PET-guided planning devices will further refine
three-dimensional conformal radiotherapy. Finally, a whole new field of application of PET in molecular biology using new radiopharmaceutics is in development. FDG, with its possibility to study
tumor glucose metabolism, has paved the way for PET in clinical oncology. It is hoped that PET examinations with new molecular tracers will allow ever better specificity and become sufficiently reliable and manageable to evaluate receptors,
transport proteins, and intracellular
enzymes so that very early response monitoring during
chemotherapy or
radiotherapy, evaluation of novel molecular-targeted
lung cancer therapies, or even gene therapy becomes possible. New tracers that have showed their promise in early clinical studies include 18F-fluorothymidine (a proliferation marker that might give better specificity in the assessment of
solitary pulmonary nodules or better accuracy in the evaluation of early response), (99m)Tc-Annexin V (
Apomate; an apoptosis-imaging agent that could be correlated with overall and progression-free survival in phase I data), or
18F-fluoromisonidazole (which can be used to quantify regional
hypoxia in human
tumors with PET).