Genitourinary Cancer

SS 30 - GU 4 - SBRT for Prostate and Renal Cancers

216 - Stereotactic Body Radiation Therapy for Unfavorable Intermediate- and High-Risk Prostate Cancer: 3-Year Outcomes of a Phase II Trial

Tuesday, October 23
4:55 PM - 5:05 PM
Location: Room 214 C/D

Stereotactic Body Radiation Therapy for Unfavorable Intermediate- and High-Risk Prostate Cancer: 3-Year Outcomes of a Phase II Trial
V. A. Macias-Hernandez1, I. Barrera-Mellado2, C. Marti1, A. Pont3, A. Fernandez-Lara1, and P. Soria1; 1Salamanca University Hospital, Salamanca, Spain, 2Faculty of Medicine, Salamanca, Spain, 3Institut Municipal d'Investigacions Mediques, Health Services Research Unit, Barcelona, Spain

Purpose/Objective(s): SBRT as monotherapy is being increasingly used for the management of low- and favorable intermediate-risk prostate cancer as a growing body of literature has shown SBRT to be safe and efficacious. However, the evidence for high-risk is based on observational studies with relatively few patients and short follow-up. Here we present 3-year CTCAE urinary (GU) and rectal (GI) toxicity, quality of life (QoL), PSA profile and biochemical/clinical progression-free survival of a phase II study focused on intermediate and high-risk patients.

Materials/Methods: cT1-3a N0 M0 prostate cancer patients without recent acute urinary retention or IPSS score >20 were eligible. Extreme hypofracionation was used to increase dose in prostate cancer to 92.3 Gy1.5 while late reponding tissues received 78.2 Gy3 over at least 2 weeks. Therefore, 8 fractions of 5.65 Gy (intermediate and high risk) or 5.48 Gy (low risk), 2-3 fractions/week, were delivered with helical tomotherapy and on-line MVCT guidance. Dose was prescribed to 95% PTV and homogeneous dose distribution into PTV (95-103%) was required. CTV=(prostate and seminal vesicles) + 0-5 mm margin. PTV=CTV + 3-6 mm margin. Endorectal balloon and bladder catheterization were introduced in 8/2015. 72% received ADT (73% neoadjuvant and 27% also adjuvant). The threshold for clinically significant worsening in the incontinence, irritative-obstructive, bowel, sexual and hormonal EPIC-26 domains was defined as ½ standard deviation below the baseline.

Results: Since 2012, 154 patients were treated. Unfavorable intermediate-, high- and very high-risk accounted for 58% of the series (90 men). Mean PSA: 13.5 ng/ml (1.2-214). Gleason 8-10: 18.1%, cT3a: 19.7%. The median follow-up was 36 months (5-72). Crude PSA relapse-free survival (2 ng/ml + nadir): 99.3% (1 unfavorable intermediate-risk patient relapsed at 29 months follow-up). Cancer-specific survival: 100%. Benign PSA bounce was seen in 2 patients. Without ADT, median PSA levels at baseline, 12, 24 and 36 months were 7.30, 0.77, 0.45 and 0.31 ng/ml, respectively. No acute or late GI Grade 3+ toxicities were observed. One late GU Grade 3 (prostatic urethra ulcer, managed conservatively) was found at 12 months. Clinically significant QoL worsening was observed in the irritative-obstructive and bowel domains, returning to baseline levels within the first year. Median age: 71.5 years (50-81). 10 men, out of 32 before SBRT, preserved erectile function at 12 months, according to the questionnaire responses.

Conclusion: Although longer follow-up is required, this slightly protracted 8-fraction regime has shown good tolerance, little impact on quality of life, and promising disease control outcomes in an unfavorable group of prostate cancer patients.
CTCAE Toxicity (%)
Acute 2 mo. 6 mo. 12 mo. 24 mo. 36 mo. 48 mo. 60 mo.
Grade
GU 1 46.4 17.7 17 17.8 14.2 11.9 5.4 0
2 19.6 5.2 2.7 1.6 2 1.4 5.4 7.6
3 0 0 0 0.8 0 0 0 0
GI 1 22.2 9.2 8.8 12.1 10.2 10.4 2.7 7.6
2 9.1 0 0.6 0.8 2 0 0 0
3 0 0 0 0 0 0 0 0
N 153 152 147 123 98 67 37 13

Author Disclosure: V.A. Macias-Hernandez: None. I. Barrera-Mellado: None. C. Marti: None. A. Pont: None. A. Fernandez-Lara: None.

Victor Macias-Hernandez

Disclosure:
No relationships to disclose.

Biography:
Victor Macias-Hernandez, Radiation Oncologist at the Valladolid University Hospital (Spain).
PhD at the University of Barcelona.
Created the Brachytherapy Unit at the Candiolo Institute for Cancer Research, Turin, in 2001.
Head of Unit at Salamanca University Hospital, Spain (2011-2018)
+15 years of experience in urological cancer.
Pioneer of prostate hypofractionated radiotherapy and SBRT in Spain.
Radiation oncology resident tutor. Lecturer at 2 masters in Radiation Oncology.
+30 articles on peer-review journals. +10 chapters books.
Principal investigator and co-investigator in clinical trials with public competitive funds.
Speaking English, French, Italian and Spanish.
Interests: Languages and cultures, swimming, piano.

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