Program Information
Treatment Planning Study of Prostate Cancer by CyberKnife with Respect to the Urethral Dose
H Mizuno*, H Mizuno , i sumida , Y Otani , m yagi , m takashina , O Suzuki , Y Yoshioka , m koizumi , k ogawa , Osaka University, Suita, Osaka
Presentations
SU-E-T-767 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:Hypo-fractionated stereotactic body radiation therapy (SBRT) with intensity modulated radiation therapy (IMRT) is nowadays one of the treatment strategies for prostate cancer. There are few reports on planning study of prostate cancer by CyberKnife with respect to the urethral dose because of the invisibility in CT. We have investigated a planning method using fixed collimators with considering dose homogeneity, conformity and urethral dose.
Methods:Radiotherapy treatment planning of prostate cancer were under a clinical trial approved by the institutional review board. The prescription dose of 35 Gy were delivered to the PTV in five fractions with the urethral catheter. Urethra position was identified by pretreatment CT and catheter, which was inserted before treatment planning CT and released after the treatment. All plans agreed to the criteria as shown in table 1, and the following constraints were recommended as well: the prescribed iso-dose line should be from 70% to 90%; the total MU should be below 50,000 MU; the minimum MU per beam should be larger than 15 MU; the estimated delivery time (excluding patient setup time) by Multiplan with image time interval of 60 s should be less than 35 min. Collimator size and position were decided as shown in figure 1. Fixed collimator of 15 mm was positioned around urethra and PTV for avoiding high dose of urethra and achieving conformity, and fixed collimator of 30 or 40 were positioned around PTV for achieving dose homogeneity.
Results:With this method, all constraints were achieved. (Table 1, Figure 2) Max dose of urethra was ranging from 103.9% to 114.2%, because urethra position was identified by pretreatment CT and urethral catheter.
Conclusion:Hypo-fractionated SBRT with IMRT utilizing urethral catheter could be a promising new treatment option for prostate cancer.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by JSPS Core-to-Core program Number 23003.
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