RADI-30. TREATMENT OF MULTIPLE BRAIN METASTASES WITH CYBERKNIFE® (CK) INITIAL EXPERIENCE AT THE RADIONCOLOGY DEPARTMENT JÚLIO TEIXEIRA SA – PORTO – PORTUGAL

Brain metastases (BM) represent an important cause of morbidity and mortality being the most common intracranial tumors in adults. Their incidence is rising for several reasons: an aging population, better systemic treatment and better diagnostic imaging techniques allowing the detection of smaller metastases in asymptomatic patients. Traditionally, the most widely used treatment for patients with multiple BM is whole brain radiation therapy (WBRT), which remains a source of debate because, although distant brain control rates have been shown to be greater with WBRT, it has no impact on overall survival and the negative effects on cognition and quality of life are higher. Radiosurgery plays a significant role in the modern management of BM. We analyzed 38 patients with multiple BM (13 with more than one treatment, totalizing 61 cases) treated with CyberKnife® (CK) in the Radioncology Department Júlio Teixeira SA, from August 2016 to February 2019, for a total of 178 lesions. The average volume was 9,2cc (0,01-73,2). Total dose ranged 18-30Gy delivered in 1–5 fractions. The average nCI was 1,23 (0,19-1,69). Tumor coverage of at least 95% was obtained by prescribing the therapeutic dose to isodose lines ranging from 69–90%. Whole brain tissue was outlined as a critical structure. The average volume of 14Gy (single fraction) and 23Gy (multiple fractions) for normal brain tissue was 6,35cc and 12,4cc, respectively. The treatment was well tolerated, with improvement or resolution of the initial neurological symptoms. Among all radiosurgical platforms the CK offers the advantage of delivering with stereotactic precision high doses of radiation without the invasive attachment of a localizing frame. As a result, in many cases, became the method of choice for treating multiple brain metastases. The attractive therapeutic profile of CK radiosurgery is reflected by a high tumor control and low toxicity allowing retreatment for recurrent metastases.