Affiliations: [a] Department of Radiation Oncology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| [b] Department of Urology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| [c] Department of Radiation Oncology, Taipei Medical University Hospital, Taipei, Taiwan
| [d] Department of Radiation Oncology, University of California, Los Angeles, CA, USA
| [e] Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan
Correspondence:
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Corresponding author: Jo-Ting Tsai, Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, No. 291, Zhongzheng Rd., Zhonghe District, New Taipei City, Taiwan 23561, Taiwan(R.O.C.). Tel.: +886 2 22490088#1352; Fax: +886 2 22490088#1369; E-mail: kitty4024@gmail.com.
Abstract: BACKGROUND AND PURPOSE: 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. MATERIAL AND METHOD: 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. RESULT: 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). CONCLUSION: 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.
Keywords: Stereotactic body radiation therapy (SBRT), prostate cancer, equivalent uniform dose (EUD), normal tissue complication probability (NTCP), cyberknife, tomotherapy
