Stereotactic body radiation therapy for adrenal oligometastases

Approximately 50% of melanomas, 30–40% of lung and breast cancers and 10-20% of renal and gastrointestinal tumors metastasize to the adrenal gland. Metastatic adrenal involvement is diagnosed by CT with contrast medium, ultrasound (which does not explore the left adrenal gland well), MRI with contrast medium and 18 FDGPET-CT which also evaluates lesion uptake. The simulation CT should be performed with contrast medium; an oral bolus of contrast medium is useful, given adrenal gland proximity to the duodenum. The simulation CT may be merged with PET-CT images with 18 FDG in order to evaluate uptaking areas. In contouring, the radiologically visible and/or uptaking lesion provides the gross tumor volume (GTV). Appropriate techniques are needed to overcome target motion. Single fraction stereotactic radiotherapy (SRT) with median doses of 16–23 Gy is rarely used. More common are doses of 25–48 Gy in 3–10 fractions although 3 or 5 fractions are preferred. Local control at 1 and 2 years ranges from 44 to 100% and from 27 to 100%, respectively. The local control rate is as high as 90%, remaining stable during follow-up when BED 10Gy is equal to or greater than 100 Gy. SRT-related toxicity is mild, consisting mainly of gastrointestinal disorders, local pain and fatigue. Adrenal insufficiency is rare.