AUTHOR=Katz Alan Jay , Kang Josephine 

TITLE=Stereotactic Body Radiotherapy as Treatment for Organ Confined Low- and Intermediate-Risk Prostate Carcinoma, a 7-Year Study

JOURNAL=Frontiers in Oncology

VOLUME=Volume 4 - 2014

YEAR=2014

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2014.00240

DOI=10.3389/fonc.2014.00240

ISSN=2234-943X

ABSTRACT=Objectives: Stereotactic body radiation therapy (SBRT) takes advantage of the prostate’s low α/β ratio to deliver a large radiation dose in few fractions. Initial studies on small groups of low-risk patients support SBRT’s potential for clinical efficacy while limiting treatment-related morbidity and maintained quality of life (QOL).  This prospective study expands upon prior studies to further evaluate SBRT efficacy for a large patient population with organ confined, low- and intermediate-risk prostate cancer patients. 
Methods:  477 patients with prostate cancer received CyberKnife SBRT.   The median age was 68.6 years and the median PSA was 5.3 ng/ml. 324 patients were low-risk (PSA < 10 ng/ml and Gleason < 7), 153 were intermediate-risk (PSA 10-20 ng/ml or Gleason = 7). Androgen deprivation therapy was administered to 51 patients for up to six months.  154 patients received 35 Gy delivered in 5 daily fractions; the remaining patients received a total dose of 36.25 Gy in 5 daily fractions.  Biochemical failure was assessed using the Phoenix criterion. 
Results:   Median follow up was 72 months. The median PSA at 7 years was 0.11 ng/ml.   Biochemical failures occurred for 11 low-risk patients (2 locally), 14 intermediate-risk patients (3 locally).  The actuarial 7-year  freedom from biochemical failure was 95.6% and 89.6% for low- and intermediate-risk groups, respectively (p < 0.012). Among patients with intermediate-risk disease, those considered to have low intermediate-risk (Gleason 6 with PSA>10, or Gleason 3+4 with PSA <10; n=106) had a significantly higher bDFS than patients with high intermediate-risk (Gleason 3+4 with PSA 10-20 or Gleason 4+3; n=47), with bDFS of 93.5% versus 79.3%, respectively.  For the low and low intermediate-risk groups, there was no difference in median PSA nadir or biochemical disease control between doses of 35 and 36.25 Gy.   
Conclusions:  CyberKnife SBRT produces excellent biochemical control rates.  Median PSA levels compare f