Stereotactic Body Radiation Therapy for Organ Confined Localized Prostate Cancer

Purpose/Objective(s): The unique radiobiology of prostate cancer supports a hypofractionated as opposed to a conventionally fractionated dose regimen with a potential for improved outcomes and reduced toxicities. We report on our continued experience using a specific robotic linear accelerator to deliver stereotactic body radiation therapy for localized prostate cancer. Materials/Methods: From April 2006 through December 2012, a total of 605 patients with localized carcinoma of the prostate were treated with stereotactic body radiation therapy using a certain robotic linear accelerator and followed at our institution. All patients had T1c to T2b disease. Two hundred eighty-five patients had low risk disease. Two hundred thirty-five patients had intermediate risk disease. Eighty-five patients had high risk disease. Pretreatment PSAs ranged from .77 to 205. Fifty patients received hormonal therapy prior to treatment at the discretion of their urologist. Treatment planning was done with CT scans fused with MRI scan except in 31 cases where MRI scan could not be done for medical reasons. Dose was prescribed to the 83% to 87% line, 5 mm beyond the capsule except posteriorly 3 mm. Five hundred twenty patients with low and intermediate risk disease received robotic radiosurgery only to a dose of 3500 to 3625 cGy over 5 fractions. Twenty high-risk patients received 4500 cGy to the pelvis followed by a boost of 2100 cGy in 3 fractions of 700 cGy each. Sixty-five high-risk patients received robotic radiosurgery only to a dose of 3500 to 3625 cGy over 5 fractions. All patients received 1500 mg of amifostine intrarectally 50 minutes prior to each fraction. Results: The median initial PSA was 8.89. The median follow-up was 24 months. The median post treatment PSA was 0.89. At the time of last follow-up, five patients have had a PSA failure by ASTRO and Phoenix biochemical definition. Three patients with intermediate risk disease failed and 2 with high risk disease failed. No patient failed locally. There were 48 patients with a minimum follow-up of at least 36 months, 24 patients had a minimum follow-up of at least 48 months, and 12 patients had a minimum follow-up of 60 months. Ninety-two patients reached a PSA below 0.2 and 146 patients reached a PSA below 0.4. The median post treatment PSA at 36 months is 0.59. The median post treatment PSA at 48 months is 0.39. The median post treatment PSA at 60 months is 0.28. One patient had hematuria which resolved with hyperbaric oxygen. Two patients required green light laser for urinary retention. Two patients had rectal bleeding which resolved with Rowasa enemas and hyperbaric oxygen. The overall survival was 100% and the biochemical disease free survival was 99%. Conclusions: Robotic radiosurgery SBRT continues to be extremely well tolerated and efficacious in the management of localized prostate cancer. Continued follow-up will be required to see if results remain durable. Author Disclosure: J. Haas: F. Honoraria; Accuray. A.E. Katz: None. M. Santoro: None. R. Ashley: None. R. Mucciolo: None. D. Kessaris: None. P. Cheetham: None. A. Sanchez: None. J. Andrews: None. M. Witten: None.