Dosimetric and radiobiological comparison of Cyberknife and Tomotherapy in stereotactic body radiotherapy for localized prostate cancer.
As recent studies have suggested relatively low α/β for prostate cancer, the interest in hypofractionated stereotactic body radiotherapy (SBRT) for prostate cancer is rising. The aim of this study is to compare dosimetric results of Cyberknife (CK) with Tomotherapy (HT) in SBRT for localized prostate cancer. Furthermore, the radiobiologic consequences of heterogeneous dose distribution are also analyzed.



A total of 12 cases of localized prostate cancer previously treated with SBRT were collected. Treatments had been planned and delivered using CK. Then HT plans were generated for comparison afterwards. The prescribed dose was 37.5Gy in 5 fractions. Dosimetric indices for target volumes and organs at risk (OAR) were compared. For radiobiological evaluation, generalized equivalent uniform dose (gEUD) and normal tissue complication probability (NTCP) were calculated and compared.



Both CK and HT achieved target coverage while meeting OAR constraints adequately. HT plans resulted in better dose homogeneity (Homogeneity index: 1.04±0.01 vs. 1.21±0.01; p = 0.0022), target coverage (97.74±0.86% vs. 96.56±1.17%; p = 0.0076) and conformity (new vonformity index: 1.16±0.05 vs. 1.21±0.04; p = 0.0096). HT was shown to predict lower late rectal toxicity as compared to CK. Integral dose to body was also significantly lower in HT plans (46.59±6.44 Gy'L vs 57.05±11.68 Gy'L; p = 0.0029).



Based on physical dosimetry and radiobiologic considerations, HT may have advantages over CK, specifically in rectal sparing which could translate into clinical benefit of decreased late toxicities.
Department of Radiation Oncology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Chun-You
CY
Chen
Department of Urology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Liang-Ming
LM
Lee
Department of Radiation Oncology, Taipei Medical University Hospital, Taipei, Taiwan.
Hsiao-Wei
HW
Yu
Department of Radiation Oncology, University of California, Los Angeles, CA, USA.
Steve P
SP
Lee
Department of Radiation Oncology, Taipei Medical University Hospital, Taipei, Taiwan.
Hsin-Lun
HL
Lee
Department of Urology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Yung-Wei
YW
Lin
Department of Urology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Yu-Ching
YC
Wen
Department of Radiation Oncology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Yi-Ju
YJ
Chen
Department of Radiation Oncology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
Chiu-Ping
CP
Chen
Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
Jo-Ting
JT
Tsai
D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
Stereotactic body radiation therapy (SBRT); cyberknife; equivalent uniform dose (EUD); normal tissue complication probability (NTCP); prostate cancer; tomotherapy