ESTRO 36 Abstract Book

S87 ESTRO 36 2017 _______________________________________________________________________________________________

Salvage HDR-BT was given in 3 fractions with weekly intervals. The target volume covered the peripheral zone of the prostate and the PET-positive area and was treated with 10 Gy per fraction. The isodose coverage of the treatment in clinical practice followed this priority: the peripheral zone> rectum> urethra> the whole gland. The biologic equivalent dose of the salvage brachytherapy in 2 Gy per fraction was 98 Gy by assuming an α/β ratio of 1.5 and 78 Gy by a α/β ratio of 3. Overall survival (OS) and biochemical failure were calculated after the salvage brachytherapy using the Kaplan- Meier method. Acute and late genitourinary and gastrointestinal toxicities were documented according to common terminology criteria for adverse events (CTCAE v 4.0). Results 22 patients had a minimum follow-up of 60 months after salvage treatment. 3 patients died after salvage treatment; causes of death were malignant melanoma, multiple organ failure and pneumonia. The 5-year OS was 95.5% with a disease-specific survival of 100% after 5 years. The 5-year biochemical control was 45%. Late grade 2 gastrointestinal toxicities were observed in 2 patients (9%). No grade 3 or higher gastrointestinal late toxicities were observed. Urinary incontinence was found in 2 patients (9%) and grade 2 obstruction of urinary tract occurred in 1 patient (4%). Conclusion Interstitial HDR brachyther apy was feasible and effective in the treatment of locally recurrent prostate cancer after definitive radiotherapy. The long-term toxicity was low and acceptable. OC-0173 Low incidence of severe toxicity by focal sa lvage HDR brachytherapy in prostate cancer recurrences M. Maenhout 1 , M. Van Vulpen 1 , M.A. Moerland 1 , M. Peters 1 , M.A.A. Van den Bosch 2 , J.R.N. Van der Voort van Zyp 1 1 UMC Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands 2 UMC Utrecht, Department of Radiology, Utrecht, The Netherlands Purpose or Objective Whole gland salvage treatment for locally recurrent prostate cancer after primary radiotherapy has a high rate of severe toxicity. The standard of care in case of a local recurrence is androgen deprivation therapy (ADT), which has significant side-effects and influence on quality of life. Focal salvage treatment might lead to acceptable toxicity and concurrently postpone or even avoid the use of ADT. Here, acute toxicity and preliminary biochemical outcomes are described after MRI-guided focal salvage high dose rate (HDR) brachytherapy in patients with radiorecurrent prostate cancer. Material and Methods 17 patients with a pathology proven local recurrence have been treated with an outpatient single fraction of 19Gy focal HDR brachytherapy in a suite equipped with a 1.5 Tesla MRI scanner for treatment guidance. Primary radiotherapy consisted of external beam radiotherapy or brachytherapy. Gross tumor volume (GTV) delineation was performed using Ga-68-PSMA or F18-Choline PET together with multiparametric 3.0Tesla MRI in all patients. A margin inside the prostate of 5 mm was added to define clinical target volume (CTV) and no margin for planning target volume (PTV) was added. Catheters were inserted under ultrasound guidance and definitive treatment planning was based on the actual MRI based catheter positions and delineations. All patients had a PSA at time of recurrence of <10ng/mL and a PSA- doubling time of ≥1 year. Toxicity was measured using the CTCAE version 4. Results

Conclusion This study confirms that mpMRI is a non-invasive technique able to characterize tumor margin in low-grade PCa. Tumor characterization and delineation is a crucial step in focal brachytherapy as only sub-volume of the prostate is treated with high gradient dose levels. Target volume margin definition is a hot topic when focal treatments (e.g. cryotherapy or HIFU) are considered and mpMRI can bring quantitative answers. OC-0172 interstitial salvage HDR-brachytherapy for recurrent prostate cancer after radiation therapy P. Jiang 1 , C. Van der Horst 2 , B. Kimmig 1 , F. Zinsser 1 , B. Poppe 3 , U. Luetzen 4 , K.P. Juenemann 5 , F.A. Siebert 1 , J. Dunst 1 1 UKSH- Campus Kiel, Department of Radiation Oncology, Kiel, Germany 2 Community Clinic Kiel, Department of Urology-, kiel, Germany 3 Medical Campus Pius-Hospital- Carl von Ossietzky University, University Clinic for Medical Radiation Physics-, Oldenburg, Germany 4 UKSH- Campus Kiel, Department of Nuclear Medicine, Kiel, Germany 5 UKSH- Campus Kiel, Department of Urology, Kiel, Germany Purpose or Objective There is growing literature on local salvage treatments following definitive radiation. However, data employing interstitial high dose rate brachytherapy (HDR-BT) for salvage treatment are rare, especially those with long- term outcomes. This is a report of our results as a unique published cohort with salvage HDR-BT after previous HDR- BT treatment (Jiang et. al. 2016, brachytherapy, paper in pressed). Emphasis was put on 5-year outcome and toxicity. Material and Methods From 2009 to 2014, 29 patients with local failure after previous radiotherapy for prostate cancer were treated with salvage interstitial HDR-BT. Primary treatment was combined external beam irradiation (EBRT) with 50Gy plus HDR-BT-boost with 30 Gy in 27 patients. The primary treatment carried the total dose to a combined biologic equivalent dose in 2 Gy per fraction of about 178 Gy, by assuming an α/β ratio of 1.5 for the tumor and about 146 Gy by an α/β ration of 3. 2 patients had undergone EBRT with 66.6 Gy of the prostate bed as salvage treatment after prostatectomy. The interval between primary treatment and salvage treatment was 5.5 years (mean ± SD: 5.5 ± 2.8 years). All 29 patients had biochemical failure according to the Phoenix definition. The diagnosis of local recurrence was made on the basis of F-18 labeled cholin-PET. The presence or co-existence of regional lymph node and/or distant metastases was excluded by imaging methods.