Genitourinary Cancer

SS 08 - GU 2 - Long-Term Updates of Prospective Prostate Cancer Clinical Trials

59 - Efficacy and Toxicity of Stereotactic Body Radiation Therapy for Localized Prostate Cancer: A Ten Year Study

Monday, October 22
7:45 AM - 7:55 AM
Location: Room 214 C/D

Efficacy and Toxicity of Stereotactic Body Radiation Therapy for Localized Prostate Cancer: A Ten Year Study
A. Katz1, and J. Kang2; 1St Francis Hospital, Roslyn, NY, 2NewYork-Presbyterian/Weill Cornell Medical Center, New York, NY

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is a newer treatment option for localized prostate cancer (PCa), with recent studies demonstrating excellent control rates and low toxicity with short to intermediate follow-up. Longer term patient outcomes demonstrating efficacy and safety, however, have not yet been previously reported. In this present study, we report 10-year outcomes for prostate SBRT in 515 patients.

Materials/Methods: Consecutively treated patients (n=515) between 2006-2009 were evaluated (median FU = 108 mos). There were 324, 153 and 38 low-, intermediate- and high-risk patients by NCCN criteria. Patients received Robotic SBRT (35-36.25 Gy in 5 fractions on consecutive days). The dose was defined to cover 95% of the Planning Treatment Volume, which was a 5 mm expansion (3mm posteriorly) of the prostate and proximal seminal vesicles. 95% of the prostate was covered by 38.5-40 Gy. Real time tracking of fiducial seeds was employed. 102 patients received ADT for up to 6 months.

Results: For the entire patient cohort, 10-year biochemical recurrence free survival (bRFS) was 93, 81 and 66% for low-, int- and high-risk patients. Biopsy proven local failure was found in 2, 6 and 10%, respectively. Favorable int-risk patients (Gleason 3+4=7 with no other int risk factors, or Gleason 3+3=6 with only one int risk factor) had excellent outcomes, with no significant difference compared to low-risk patients (10y DFS 89 vs 93%, P=0.3). Unfavorable int-risk patients had outcomes similar to high-risk patients (10y bDFS of 63 vs 66%, P=0.8). PSA and Gleason score were the only significant factors predicting for bRFS on multivariate analysis (P<0.002) with dose, ADT not significant. Toxicity was overall mild. There was significantly higher late G2-3 GU toxicity with 36.25 Gy compared to 35 Gy (14.6 vs 8.2%, P=0.04), but no difference in G2 GI toxicity. Mean EPIC QOL urinary and bowel domains for all patients declined during the first 3 months and then returned to baseline. Mean sexual QOL scores declined by 40% at 10 years

Conclusion: In conclusion, prostate SBRT continues to demonstrate excellent biochemical and local control rates with low toxicity and excellent QOL with now 10 years of follow up. Our results are at least as favorable as other forms of radiation therapy. We continue to find 35 Gy to be as effective as 36.25 Gy, with significantly lower GU toxicity, suggesting 35 Gy may be a preferable dose for patients with low- and favorable int-risk disease. Long-term results of prospective studies are needed to validate our findings. For higher risk patients, the use of ADT failed to demonstrate improvement in long-term disease control. Given that most SBRT failures were not local, we hypothesize that dose escalation will not translate to improved bFRS, and strategies to reduce systemic failures should be explored.

Author Disclosure: A. Katz: None.

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