Lower fluorodeoxyglucose positron emission tomography maximum standardized uptake value may show a better response to stereotactic body radiotherapy of adrenals in oligometastatic disease

Introduction: Stereotactic body radiotherapy (SBRT) is well established for oligometastatic disease, and it is increasingly used to treat adrenal metastases. Material and methods: In this retrospective study we performed an analysis of 75 metastatic adrenal lesions in 64 patients with oligometastatic disease. According to the fluorodeoxyglucose positron emission tomography/ computed tomography (FDG PET/CT) maximum standardized uptake value (SUVmax) of adrenal metastases, patients were categorized into three groups: low, intermediate, and high SUVmax. Results: For all clinicopathological characteristics we found significant relationships for levels of SUVmaxand objective response rate (Kendall Tau -c = 0.290; p = 0.017). Patients who responded to SBRT had a significantly lower SUVmax value than those who did not respond (7.6 +/- 2.4 vs. 9.7 +/- 3.8; p = 0.015). At the appropriate SUVmax cut-off values, the biomarker distinguished between patients with and without a response significantly and moderately (area under the curve = 0.670, 95% confidence intervals: 0.540-0.790; p = 0.015). Conclusions: Lower SUVmax is associated with a better response to SBRT in patients whose disease progressed mainly in the adrenal glands.