International Journal of Radiation Oncology*Biology*Physics
Poster Viewing AbstractPhase 1 Study of Increased Dose-per-Fraction Hypofractionated Radiation Therapy Following Radical Prostatectomy: Toxicity Assessment of 15 Fractions at 3.6 Gy per Fraction
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Purpose/Objective(s)
Although multiple Phase I/II studies demonstrate safety and low rates of toxicity following SBRT to the intact prostate, there are limited data on hypofractionation after prostatectomy. This Phase I study was performed to evaluate acute toxicity associated with dose escalation to the prostate bed in the post-prostatectomy treatment of prostate cancer. We hypothesize that the toxicity of escalating the dose per fraction, while decreasing the number of fractions, to the prostate fossa in the
Materials/Methods
This study was designed to look at acute toxicity, defined as toxicity that occurred within the first 10 weeks of RT, of different dose fractionation schemes. The doses chosen for this study are based on an equivalent biological effective dose to a previously published hypofractionated post-prostatectomy study that showed no increase in acute bowel or bladder toxicity. The dose levels are: Level 1 -3.6 Gy x 15fractions; Level 2- 4.7 Gy x 10 fractions; Level 3 - 7.1 Gy x 5 fractions. Dose
Results
Six patients were enrolled at the first dose level. The median age of the patients was 64 years of age. The Median PSA at time of enrollment was 0.135 ng/mL (range 0.03ng/mL – 0.36ng/mL). The median time from prostatectomy to enrollment was 7 months. None of the six patients received concurrent ADT. Grade 1 urinary frequency was seen in all 6 patients. Four of 6 patients experienced grade 1 urgency, and 3/6 patients experienced grade 1 fatigue. Four of 6 patients started radiation therapy with
Conclusion
Patients tolerated 3.6 Gy x 15 fractions to the prostate fossa with minimal acute toxicity. Dose-escalation will proceed to 4.7Gy x 10 fractions to the prostate fossa.
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Author Disclosure: L.K. Ballas: None. M. Aron: Employee; USC Department of Pathology. E. Chung: None. I. Shuryak: None. T.B. Dorff: None. D. Yang: None. D.J. Brenner: None. S. Groshen: None.