Changes in Glucose Metabolism during and after Radiotherapy in Non-Small Cell Lung Cancer

Abstract

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]fluorodeoxyglucose were performed before (PET0), during (PET1; at a median of 14 days before the end of radiotherapy) and after the end of radiotherapy (PET2 and PET3, 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 PET1 (7.9 ± 4.8), PET2 (5.1 ± 4.1) and PET3 (2.7 ± 3.1) were all significantly (P <0.05; ANOVA repeated measures) lower than at PET0 (16.1 ± 10.1). Standardized maximum uptake at PET1 was significantly higher than at both PET2 and PET3. There were no significant differences in SUVmax between PET2 and PET3. PET3 identified 4 complete and 2 partial metabolic responses, whereas PET1 identified 6 partial metabolic responses. Radiotherapy-induced increased [18F]fluorodeoxyglucose uptake could be visually distinguished from tumor uptake based on PET/CT integration and was less frequent at PET1 (n = 2) than at PET3 (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 [18F]fluorodeoxyglucose images, particularly when using PET/CT.