The role of FDG uptake to predict the need for re-irradiation in patients treated with 8 Gy (X-ray) single fraction palliative radiotherapy for bone metastases

The study aims to evaluate the relationship between the maximum standardized uptake value (SUVmax) of fluorodeoxyglucose positron emission tomography (FDG-PET) before radiation therapy (RT) and the further need for re-irradiation (re-RT) in patients with bone metastases (BM), and to predict the complete response using pre-treatment SUVmax.

Fifty-three patients with 133 painful BMs were accepted into the study. Pain scores and SUVmax at painful BM were recorded. Eight Gray in single fraction palliative RT was administered to all of the patients. A total of 7 patients (8 osseous lesions) underwent re-RT.  Factors associated with re-RT were analyzed using Cox regression analysis.

The ideal SUVmax cut-off to predict complete response was 7.95. Median SUVmax was 12.75 (±4.1) and 7 (±3.36) in patients who required re-RT due to pain progression and in those who did not, respectively (p<0.001).

FDG uptake may be predictive of the need for re-RT in patients with painful BM. This may impact decisions with single-fraction RT which is associated with higher rates of partial response and further need for re-RT at the same location in patients with high SUVmax. Pre-treatment FDG uptake also may be useful in predicting a complete response.