ESTRO 37 Abstract book

S1249

ESTRO 37

EP-2260 High dose rate brachytherapy delivered in two fractions within one day for prostate cancer N. Gorka 1 , J.L. Lopez Guerra 2 , E. Krumina 3 , H. Marsiglia 4 , M. Vila 3 , A. Miró 3 , A. Garcia 3 , E. Gómez 3 , I. Azinovic 5 1 SEOR, San Francisco de Asís, MADRID, Spain 2 University Hospital Virgen del Rocio, Department of Radiation Oncology, Seville, Spain 3 Instituto Alicantino de oncología-Imoncology, Department of Radiation Oncology, Alicante, Spain 4 Instituto Oncológico FALP, Department of Radiation Oncology, Santiago de Chile, Chile 5 Imoncology, Department of Radiation Oncology, Madrid, Spain Purpose or Objective High dose-rate (HDR) brachytherapy (BT) is a highly conformal method of dose delivery and safe dose escalation to the prostate. There are radiobiological advantages over external beam radiotherapy. The purpose of this study is to determine the toxicity of the treatment protocol of 13.5 Gy x 2 fractions . Material and Methods From 2010 through 2017, 119 patients, 84 (71%) with low- risk, 25 (21%) with intermediate-risk, and 10 (8%) with high-risk prostate cancer, were treated with HDR-BT as monotherapy. Pretreatment International Prostatism Symptom Score (IPSS) and International Index of Erectile Function (IIEF-5) categorized urinary symptoms and erectile dysfunction as moderate in 29% and 24% of patients, respectively. No patient had severe (IPSS ≥20) urinary symptoms and 26% showed severe (IIEF-5 ≤7) erectile dysfunction. Dose fractionation was 13.5 Gy/2 fractions within one day for all patients. The estimated biologic equivalent dose (BED) of 27 Gy from this treatment is 261 Gy (using α/β ratio of 1.5 Gy). Of these patients, 80 (67%) did not receive androgen deprivation therapy. ADT was administered to, respectively, 17%, 76%, and 60% of the low-, intermediate-, and high-risk patients. Median follow-up time was 4.4 years (range, 0.8-6.3 years). Results Median age at diagnosis was 66 years (range 45-84). Respective actuarial rates of no biochemical evidence of disease, overall survival, and metastasis-free survival for all patients were 96%, 98%, and 98%, respectively. The cumulative incidence of acute grade 2 and 3 genitourinary (GU) toxicity at was 9% and 2%, respectively. Median post-BT prostate-specific antigen (PSA) nadir level was 0.08 (range, 0.01-1.40). Univariate analysis showed that older patients (OR: 0.24; P <0.001) and those receiving ADT (OR: 0.24; P <0.001) associated with lower post-BT PSA levels (OR: 0.40; P =0.027) but only the age retained significance after multivariate analysis (OR: 0.27; P =0.002). The corresponding incidences of late GU toxicity were 18% and 1%. There was only one case that experienced GI toxicity (late grade 2). No grade 4 or 5 of either type of toxicity was detected. Multivariate analysis showed that having moderate to severe IPSS (OR: 4.01; RP =0.023) or higher V100 (OR: 60.14; P =0.037) associated with higher acute GU toxicity. Patients with moderate to severe IPSS at baseline had GU toxicity in 35% of cases compared with 15% in those patients with mild symptoms. Patients with higher V100 had GU toxicity in 31% of cases compared with 10% in those with lower V100. Additionally, patients having a higher T stage (≥T2a) associated with lower grade ≥1 (21% vs 42%; OR: 0.4; P =0.042) and ≥2 (9% vs 25%; OR: 0.3; P =0.05) late GU toxicity compared with T1c patients. Conclusion The findings of this study show that HDR-BT 13.5 Gy x 2 as monotherapy was safe and effective for prostate cancer patients mostly with low-intermediate risk. T stage and prostate V 100 seem to associate with GU toxicity.

EP-2261 A single centre experience of HDR brachytherapy as salvage treatment for relapsed prostate cancer E. Dugdale 1 , F. Slevin 1 , S. Rodda 1 , D. Bottomley 1 , B. Carey 2 , J. Smith 2 , O. Hulson 2 , E. Adiotomre 2 , J. Mason 3 , P. Bownes 3 , A. Henry 1 1 St James Institute of Oncology, Clinical Oncology, Leeds, United Kingdom 2 St James Institute of Oncology, Radiology, Leeds, United Kingdom 3 St James Institute of Oncology, Medical Physics & Engineering, Leeds, United Kingdom Purpose or Objective High Dose Rate (HDR) brachytherapy (BT) can be used as salvage treatment for men whose prostate cancer has recurred locally following previous radiation. The work documents characteristics of treated patients and clinical outcomes. Material and Methods Retrospective single centre review of HDR salvage BT cases performed between 2010 and 2016. A real-time trans-rectal US HDR technique is used with the PTV based on cognitive fusion of multi-parametric MRI images and information from targeted biopsy. Demographic and clinical data were collected prospectively in an in-house BT database and electronic patient records were reviewed. Patients are followed up 6 monthly following salvage BT. Until 2012 the salvage dose was 30Gy in 3 fractions (5 patients). The subsequent 17 patients were treated with focal salvage BT in single 19Gy fraction (Focal PTV D90 >17.1Gy). 1 man received a single 15Gy fraction to the whole gland. Use of additional hormonal therapy is at clinician’s discretion. Results 23 men underwent salvage HDR BT for relapsed non- metastatic prostate cancer from 2010-16. All had pelvic MRI and 12 had additional Choline-PET scans to exclude distant disease. Recurrence was confirmed using template biopsy and found to be intra-prostatic in 18, isolated within seminal vesicles in 4 and isolated peri- prostatic in 1. Patient characteristics both at initial treatment and salvage BT are shown in Table 1.

The median time from initial to salvage treatment was 100.3 months (range 35.9–149.3 months). Median PSA at salvage was 4.5 (range 1.1–9.4) ng/mL. Hormonal therapy with salvage BT was used in 18/23 men, with majority for 6 months (15 men) and the remainder long-term. Dosimetric analysis for the 17 patients treated with focal salvage BT shows the median Focal PTV D90 was 18.4Gy (range 15.1–20.4Gy). Rectal dose constraints were achieved in all (D2cc rectum <12.35Gy) and urethra constraints were met in all but 5 men (D10 <17.1Gy). In 3 men the Focal PTV D90 was reduced to ensure rectal/urethral dose limits were achieved. Median length of follow up is 18.4 months (range 0.8–80.3 months). 2 year PSA progression free survival is 55.34% (CI 25.8-77.2). Image 1.