ESTRO 36 Abstract Book

S89 ESTRO 36 _______________________________________________________________________________________________

Results In all treatments constraints to rectum, bladder and urethra were met. Average dose to the treatment volume was D95: 18.9Gy (SD 2.4Gy). On average 9.4 catheters (range 6-13) were used. Treatment volume was on average 7.4cc (SD2.9cc). With a median follow-up of 6 months (range 1-24 months) a biochemical recurrence according to Phoenix criteria (rise of > 2 ng/mL) had occurred in 1 of 17 patients. There was one patient with late grade 3 urinary incontinence toxicity. Conclusion Focal salvage treatment for local recurrence after primary external beam radiotherapy or brachytherapy is an effective treatment modality with regards to acute toxicity. Whether this treatment option might lead to cure or successfully postpone ADT with acceptable long term toxicity needs further investigation. OC-0174 Salvage LDR-brachytherapy for recurrent prostate cancer: results from a single institution S. Magrini 1 , F. Barbera 1 1 Spedali Civili di Brescia, Department of Radiation Oncology "Istituto del Radio", Brescia, Italy Purpose or Objective To evaluate the results of whole gland salvage brachytherapy (SBT) after primary external beam radiotherapy in terms of toxicity/QoL and efficacy. Material and Methods We retrospectively analyzed the clinical data of 19 patients consecutively treated with SBT at our Institution from June 2012 through November 2015. Local recurrences were identified with 11C-Choline PET/CT and MRI after biochemical recurrence according to Phoenix criteria. The prescription dose was 130Gy-LDR-BT to the whole prostate gland. Acute and late toxicities were graded with the CTCAE-4.0 scoring system. Data from IPSS (International Prostatic Symptoms Score) and IIEF (International Index of Erectile Function) questionnaires at baseline and at 6, 12 and 24 months after SBT were also reported (higher IPSS and lower IIEF indicate deterioration). Univariate analysis was done to identify predictors of biochemical control and toxicities. Results Median follow up after SBT was 24 months. Observed severe late toxicities were as follows: 2/19 G3 cystitis (10,2%) and 1/19 G4 proctitis (5,3%). Median IPSS scores pre-SBT and after 6,12,24 months were respectively 4,11,12 and 5. Median IIEF score pre-SBT and after 6,12,24 months were respectively 5,2,4 and 4. At the time of analysis 2/19 patients showed biochemical relapse (3- years-FFBF 85,2%). At univariate analysis only interval to relapse after primary EBRT < 70 months (p=0,05) and PSA reduction between pre-and post SBT level > 80% (p=0,008) were significantly related to further biochemical failure. No statistically significant correlations were found between IPSS and IIEF score before SBRT and post treatment toxicity. Conclusion SBT for recurrent prostate cancer after primary EBRT seems to be a feasible treatment for selected patients. The severity of the observed toxicities shows a peak after 6 months/1 year after local re-treatment and then decreases. Early FFBF rates are good. These preliminary results suggest further accrual of patients and the collection of longer term data. OC-0175 Salvage HDR-BT in prostate local recurrence after radiation therapy: Retrospective analysis C. De la Pinta 1 , T. Muñoz 1 , C. Vallejo 1 , S. Sancho 1 , F. López 1 , M. Martin 1 , A. Hervás 1 1 Hospital Ramon y Cajal, Radiation Oncology, Madrid, Spain

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.