ESTRO 37 Abstract book

S1250

ESTRO 37

study can apply for other tumors such as cervical cancer, however further results are underway. EP-2263 Hypofractionated radiotherapy and single fraction brachtherapy boost in prostate cancer: L. Larrea 1 , E. López-Muñoz 2 , P. Antonini 2 , V. González- Vidal 2 , M.C. Baños 3 , J. Bea 3 , M.A. García 3 1 Clinica Virgen del Consuelo, Radiation Oncology, Valencia, Spain 2 Clínica Virgen del Consuelo, Radiation Oncology, Valencia, Spain 3 Clínica Virgen del Consuelo, Radiophysics Department, Valencia, Spain Purpose or Objective To evaluate local control rate and radiation toxicity in patients with intermediate and high-risk prostate cancer treated with hypofractionated external beam radiotherapy plus high-dose-rate brachytherapy (HDR) boost. Material and Methods 95 patients with prostate cancer were treated between 2013 and 2017 at Hospital Vithas-Nisa Virgen del Consuelo in Valencia, Spain. Median PSA at diagnosis was 9.69 ng/ml (range 2.4-35). According to NCCN risk classification; 49.4% were intermediate and 48.3% high- risk prostate cancer. CT scan and bone scintigraphy were mandatory in all high-risk prostate cancer and both were negative in all of our patients. Unfavorable intermediate and all of high-risk patients (56.2%) received at least 6 months of deprivation androgen therapy (ADT). Prescription dose in hypofractionated external beam radiation was 36 Gy in 12 fractions (five fractions per week). CTV in intermediate risk was prostate in cases with tumour confined in prostate gland. In high-risk patients with seminal vesicles involved (T3b), these were included in the treated volume. PTV was the CTV plus a 5 mm in all margins except in posterior wall where it was 2 mm. External beam radiation was delivered using intensity-modulated technique (IMRT) or volumetric modulated arc therapy (VMAT) with daily ConeBeam IGRT . HDR brachytherapy boost was provided before or after external radiotherapy. Under spinal anesthesia, patient in lithotomy position, ultrasound guided intersticial technique . The brachytherapy PTV was defined for prostate with a 2 mm margin in all directions. Prescription dose was 15 Gy to the 100% of the PTV. The HDR source used was 192 Iridium from Flexitron Elekta ® . It´s an ambulatory procedure that expends less than 3 hours. The assessment of gastrointestinal (GI) and genitourinary (GU) toxicity was according to Common Terminology Criteria for Adverse Events (CTCAE) v 4.0. Results Median patient age was 68.2 years (range 47-80). With a median follow-up of 29.2 months (range 2-51 months) local control rate was 100%. One patient died of renal tumour and three patients presented disease progression outside of irradiated areas; two with lymph nodal relapse and one bone solitary metastases. Median PSA 1 year after treatment is 0.42 (range 0.0-3.4) for patients with the disease under control. Median number of vectors used in brachytherapy was 13 (range 8-16). Using CTCAE v 4.0 toxicity scale, acute transient GU and GI toxicity G1 and G2 were seen in 56.6% and 13.4% of patients. Late GU and GI toxicity were presented in 20.1% and 7.2%. No acute and late GU and GI G3-G4 toxicity were reported. Sexual function was preserved in 87.6% of patients after Our results show that combined treatment with hypofractionated radiation therapy and high-dose-rate brachytherapy boost is a safe and well-tolerated technique with high local control rate and low radiation toxicities. Longer follow-up is needed to confirm these early results. treatment. Conclusion

7 men have had post-salvage PSA progression (nadir+2 definition) with median time to progression of 15.5 months (range 7.25–65.4 months). One has confirmed metastatic disease and 4 have had changes in hormonal therapy. Grade 2 (CTCAEv4.0) genito-urinary toxicity at 6 months has been found in 5 patients (3 incontinence, 1 haematuria, 1 urethral stricture). Conclusion Early outcomes in this cohort suggest acceptable toxicity with salvage HDR BT. Longer term rates of biochemical control remain to be discerned in this group of men, the majority of whom had additional hormonal treatment. EP-2262 Novel application of Gold-Nanoparticles in prostate LDR brachytherapy cancer treatment H. Safigholi 1 1 Department of Electronic Engineering, Shiraz branch- Islamic Azad University, Shiraz, Iran Islamic Republic of Purpose or Objective Recently low dose rate brachytherapy technique in combination with gold nanoparticles (GNPs) is a promising technology to boost the dose in prostate tumor cells. Here a novel approach for prostate LDR brachytherapy cancer treatment is proposed to increase the dose in high-risk prostate target volume (HRCTV) while simultaneously decrease the dose to organs at risk Firstly, Monte Carlo MCNP6 code was used to calculate the TG-43U1 dose of a single Pd-103 (IsoAid Advantage TM ) brachytherapy seed in an infinite water phantom. Secondly, 90 seeds with 1 cm seed to seed distances are simulated in a high-risk standard prostate phantom, while the rectum and urethra organ at risk (OARs) volumes are delineated. In the next step, another MC calculations for a homogeneous concentration of 20 mg/g GNPs in a high- risk prostate volume performed. Finally, dose volume histogram (DVH) parameters such as D90, V100, and V200 for HRCTV and D5 and V100 for OARs with and without GNPs are evaluated. Results In total dose to HRCTV were increased (~145%), while at the same time dose to the OARs due to the shielding effect of GNPs were decreased (35% in urethra, and 42% in rectum). The D90, V100, and V200 of HRCTV with (without) GNPs were achieved 250 Gy (101 Gy), 99.9% (98.2%), and 95% (52%), respectively. The D5 and V100 for urethra OAR with (without) GNPs were 301 Gy (470 Gy) and 19.1% (86.2%), respectively. These corresponding values for rectum OAR with (without) GNPs were obtained 65 Gy (115 Gy) and 0% (6.5%) respectively. Conclusion GNPs combination with LDR low dose energy brachytherapy technique for prostate tumor cure is a new promising technology with a synergy of increasing dose to HRCTV and simultaneity OARs sparing. The findings in this (rectum and urethra). Material and Methods