Radiotherapy for aneurysmal bone cysts. A rare indication

Aneurysmal bone cysts (ABC) are rapidly growing benign osseous lesions composed of blood-filled channels separated by fibrous septa. Since the value of external beam radiotherapy (EBRT) for ABC has not been well defined, the German Cooperative Group on Radiotherapy for Benign Diseases performed the national register study described herein. Five German institutions collected data regarding clinical features, treatment concepts, and outcome for patients with ABC who had been referred for local EBRT over the past 30 years. Between 1990 and 2015, 10 patients with ABC were irradiated (5 female/5 male). Median age was 23 years (range 14-40 years). Involved sites were: spine (n = 3), sacrum/pelvis (n = 2), shoulder/scapula (n = 2), humerus (n = 1), femur (n = 1), and radius (n = 1). The median EBRT total and fractional doses were 28 Gy (range 5-40 Gy) and 2 Gy (range 1-2 Gy), respectively. Median follow-up was 65 months (range 12-358 months). Persistent pain relief was achieved for all patients. However, long-term follow-up response data were only available for 7/10 patients. All 7 patients exhibited a radiological response and experienced no recurrent disease activity or pain during follow-up. Acute and late radiogenic toxicities ≥ grade 3 and secondary malignancies were also not observed. Primary or adjuvant EBRT seems to be an effective and safe treatment option for persistent or recurrent ABC. Fractionated doses below 30 Gy may be recommended. (orig.)