© 2015 INTM, Italy. Published by Wichtg Publishing TJ ISSN 0300-8916 Tumori 2015; 101(6): 684-691 Original research article guidelines. Surgery and radiaton therapy, either adminis- tered as brachytherapy or external beam radiaton therapy, are commonly used in the treatment of prostate cancer, and androgen deprivaton therapy (ADT) may be added selectve- ly for certain cases in intermediate to very high risk groups. Moreover, external beam radiotherapy has the advantage of being noninvasive, and it is not inferior to radical prostatec- tomy or brachytherapy in the curatve treatment of localized prostate cancer (3). External beam radiaton therapy can deliver radiaton to patents with prostate cancer using 3D conformal radio- therapy (3DCRT), intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), or stereotactc ablatve radiotherapy (SABR). Stereotactc ablatve radio- therapy required highly conformal technique in order to de- liver high-dose radiaton in 5 or fewer treatment fractons to prevent toxicity (4). The CyberKnife system (Accuray, Sunnyvale, CA, USA) consists of a 6 MV linear accelerator mounted on a robotc arm with 2 orthogonal radiographic imaging cameras that track fducial markers in the prostate. The CyberKnife can produce SABR to prostate cancer with a treatment plan conformality that is superior to IMRT (5). Compared to VMAT by RapidArc (Varian Medical Systems, Palo Alto, CA, USA), the CyberKnife has no discernible do- simetric advantage (6, 7). However, the CyberKnife has the DOI: 10.5301/tj.5000355 Stereotactc ablatve radiotherapy with CyberKnife in the treatment of locally advanced prostate cancer: preliminary results Chao-Yueh Fan, Hsing-Lung Chao, Wen-Yen Huang, Chun-Shu Lin, Chang-Ming Chen, Cheng-Hsiang Lo Department of Radiaton Oncology, Tri-Service General Hospital, Natonal Defense Medical Center, Taipei, Taiwan - ROC Introducton Prostate cancer has the highest prevalence among all can- cer types in men and is the second leading cause of cancer death in men, resultng in an estmated 30,000 deaths in the United States in 2014 (1). To simplify the treatment recom- mendatons and prognostcaton, D’Amico et al (2) proposed risk classifcaton, which stratfes patents with clinically local- ized prostate cancer into 3 risk groups, which has been modi- fed by the Natonal Comprehensive Cancer Network (NCCN) abstract Aims and background: Recent clinical reports of stereotactc ablatve radiotherapy (SABR) in the treatment of low-risk prostate cancer have been encouraging. Our study evaluates the efcacy and safety of SABR using the CyberKnife system for treatng intermediate- to very-high-risk prostate cancer. Methods and study design: Between May 2010 and June 2013, 31 patents (15 intermediate risk, 14 high risk, and 2 very high risk) without pelvic lymph node metastasis were enrolled retrospectvely. The treatment consist- ed of 37.5 Gy in 5 fractons over 1-2 weeks using CyberKnife SABR. Twenty-fve patents (81%) received androgen deprivaton therapy (ADT). Biochemical failure was defned using the nadir + 2 criterion. Toxicity was assessed with the Common Terminology Criteria of Adverse Events (version 4). Results: The median follow-up was 36 months (range 7-58 months). The median pretreatment prostate-pecifc antgen (PSA) was 13.5 ng/mL (range 4.5-124.0 ng/mL). The median PSA decreased to 0.09 ng/mL (range <0.04-5.38 ng/mL) and 0.12 ng/mL (range <0.04-2.63 ng/mL) at 6 months and 12 months afer SABR, respectvely. The 3-year biochemical relapse-free survival was 90.2% for all patents, 100% for the intermediate-risk patents, and 82% for the high- and very-high-risk patents (p = 0.186). No patent experienced ≥ grade 3 toxicity. There were 7 acute and 5 late grade 2 genitourinary toxicites and 1 acute and no late grade 2 gastrointestnal toxicity. Conclusions: Our preliminary results support that CyberKnife SABR with ADT is safe and feasible in patents with intermediate- to high-risk prostate cancer. A further large-scale clinical trial with longer follow-up is warranted. Keywords: Biochemical response, CyberKnife, Prostate cancer, Stereotactc ablatve radiotherapy, Toxicity Accepted: April 28, 2015 Published online: May 21, 2015 Corresponding author: Hsing-Lung Chao Department of Radiaton Oncology Tri-Service General Hospital Natonal Defense Medical Center No. 325, Sec. 2 Chenggong Rd Neihu District Taipei City 114 Taiwan, ROC popo12211221@yahoo.com.tw