(P079) Linac-Based SBRT Delivered in Five Fractions for Definitive Prostate Cancer Treatment Using VMAT and Flattening Filter-Free Beams: The Phase II Lankenau Experience

April 15, 2014
Oncology, Oncology Vol 28 No 1S, Volume 28, Issue 1S

To evaluate the feasibility and toxicity of hypofractionated stereotactic body radiation therapy (SBRT) with volumetric modulated arc therapy (VMAT) and flattening filter-free (FFF) beams.

Saritha Ravella, MD, Albert S. DeNittis, MD, MS, Harry Hu, MS, Lori DeNittis, RTT, David Wang, PhD; Lankenau Medical Center

Background: To evaluate the feasibility and toxicity of hypofractionated stereotactic body radiation therapy (SBRT) with volumetric modulated arc therapy (VMAT) and flattening filter-free (FFF) beams.

Methods: A prospective National Cancer Institute (NCI)-designated phase II study was approved by our institutional review board (IRB) (started in October 2011). Inclusion criteria were histologically proven prostate adenocarcinoma, Gleason Score 6–7, clinical stage T1b–T2b, prostate-specific antigen (PSA) ≤ 20 ng/mL, prostate volume ≤ 100 cc, Eastern Cooperative Oncology Group (ECOG) performance status 0–1, no prior prostatectomy, cryotherapy, or radiotherapy to the prostate. SBRT was delivered at a prescribed planning target volume (PTV) dose of 36.25 Gy in five fractions using the TrueBeam STx. Patients self-reported on validated quality of life (QOL) measures, such as American Urological Association (AUA) Index, Sexual Health Inventory for Men (SHIM), Utilization of Sexual Medications/Devices (USMD), Expanded Prostate Cancer Index Composite Short Form (EPIC-26) with five components (urinary irritative, urinary incontinence, bowel, sexual, and hormonal), and Short Form-12 (SF-12) with two components (physical and mental). Patients were analyzed at predefined time intervals.

Results: A total of 25 patients have been recruited to date. Mean age of the patients was 68 years (range: 52–80 yr). Mean Gleason score was 6.32 (range: 6–7). Mean PSA was 6.45 ng/mL (range: 0.63–18.7 ng/mL). All patients tolerated the treatment well with no acute adverse effects, as noted on their QOL questionnaires. Evaluating patients in a time period ranging from 6 to 24 months, the EPIC-26 showed a significant difference using the Kruskal-Wallis Test between average total score at pre-entry when compared with 1-month, 6-month, and 12-month evaluations. however, mean pre-entry score was not significantly different from mean score at 24 months, demonstrating a transient decline in the bowel-related QOL. Also patients’ perception of bowel urgency showed no impact on QOL on the EPIC-26.

Conclusion: Early findings indicate that SBRT with VMAT and FFF beams for low–intermediate-risk prostate cancer delivered in five fractions is feasible and tolerated well. Long-term follow-up is needed for assessment of late toxicity and outcomes.