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 SUV_max 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.