Changes in glucose metabolism during and after radiotherapy in non-small cell lung cancer

Aims and background. Evaluation of the metabolic response to radiotherapy in non- small cell lung cancer patients is commonly performed about three months after the end of radiotherapy. The aim of the present study was to assess with positron emission tomography/computed tomography (PET/CT) and [ ¹⁸F]fluorodeoxyglucose changes in glucose metabolism during and after radiotherapy in non-small cell lung cancer patients. Methods and study design. In 6 patients, PET/CT scans with [ ¹⁸F]luorodeoxyglucose were performed before (PET ₀), during (PET ₁ at a median of 14 days before the end of radiotherapy) and after the end of radiotherapy (PET ₂ and PET ₃, at a median of 28 and 93 days, respectively). The metabolic response was scored according to visual and semiquantitative criteria. Results. Standardize maximum uptake at PET ₁ (7.9 ± 4.8), PET ₂ (5.1 ± 4.1) and PET ₃ (2.7 ± 3.1) were all significantly (P 0 (16.1 ± 10.1). Standardized maximum uptake at PET, was significantly higher than at both PET ₂ and PET ₃. There were no significant differences in SUV _miX between PET ₂ and PET ₃. PET ₃ identified 4 complete and 2 partial metabolic responses, whereas PET ₁ identified 6 partial metabolic responses. Radiotherapy-induced increased [ ¹⁸Fl]luorodeoxyglucose uptake could be visually distinguished from tumor uptake based on PET/CT integration and was less frequent at PET ₁ (n = 2) than at PET ₃ (n 6). Conclusions. In non-small cell lung cancer, radiotherapy induces a progressive decrease in glucose metabolism that is greater 3 months after the end of treatment but can be detected during the treatment itself. Glucose avid, radiotherapy-induced inflammation is more evident after the end of radiotherapy than during radiotherapy and does not preclude the interpretation of 1'8Flfluorodeoxyglucose images, particularly when using PET/CT.