[18-FDG positon emission tomography and distal metastasis from lung cancer]

"Whole body" FDG-PET usually covers the body from the base of the skull to the upper third of the thighs, arms in abduction. Thus, the upper part of the head and the lower limbs are not included in the acquisition field. We report the cases of three patients with non-small-cell lung cancer who developed secondary distal localizations beyond the acquisition field of "whole body" FDG-PET. Lung cancer is known to favor hematogenic dissemination, raising the possibility of early distal metastasis. A pretherapeutic PET scan which includes the extremities can be useful to search for distal extension. These true whole body scans are time consuming and can thus limit machine availability. Furthermore, the diagnostic yield of this type of examination may be low since it can be estimated that about 1% of patients will develop isolated distal metastases (3 out of 293 patients in our series initially treated for non-metastatic non-small-cell lung cancer). In the current context of technical availability, systematic inclusion of the lower limbs in the PET scan acquisition field would not appear warranted for the initial work-up of patients with non-small-cell lung cancer. However, clinicians must be aware that distal metastases (brain, lower limbs) may not be detected.