ESTRO 38 Abstract book

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rate brachytherapy (HDR-BT) treatment, plesiotherapy modality, with custom-made moulds. Material and Methods 87 pts out of 198 pts (44%) were treated with HDR-BT in our Department (110 NMSC lesions) from May 2015 to May 2017 with custom-made moulds. HDR-BTtreatment (6 Gy/fraction; total dose 42 Gy) was used in 88.2% pts with an equivalent 2 Gy dose (EQD2) of 56 Gy. All the lesions were limited 3-4 mm depth. The median age was 79 years old (range 29-97), 60% of pts were males and 40% females. Basal-cell carcinoma (90%) was the most frequent histological type. 80.9% of the lesionswere T1 stage (80.9%) and 100% were located on face and forehead. Treatment intention was radical in 83.6% of the pts and adjuvant in the 16.4%. Results The median follow-up was 31 months (range 9-65). LDFS was 95.45%. There were no differences in terms of local control related to tumour stage (p 0.149.Pts had acute skin toxicity grade 1 (62.7%) and grade 2 (29.1%). Conjunctival toxicity appeared in 15.5 % (lesions near to the eyes). Cosmetic results were considered excellent and good in all of the patients. Conclusion In base to our initial results, plesiotherapy with custom- made moulds is a safe, attractive and a good alternative of treatment in NMSC. This modality of treatment provides excellent results in terms of local control and cosmesis. PV-0145 The impact of modern imaging on low dose- rate prostate brachytherapy D. Lamb 1 , L. Greig 2 , G. Russell 3 , J. Nacey 4 , L. Woods 5 1 Victoria University of Wellington, School of Biological Sciences, Wellington, New Zealand ; 2 Capital and Coast District Health Board, Radiation Physics, Wellington, New Zealand; 3 Southern Cross Hospital, Prostate brachytherapy, Wellington, New Zealand; 4 University of Otago, Surgery, Wellington, New Zealand; 5 Victoria University, Statistics, Wellington, New Zealand Purpose or Objective To determine if modern imaging has improved our understanding of why biochemical failure (BF) and urethral stricture develop in some men after low dose-rate A prospectively maintained database containing information on 951 men with early stage prostate cancer treated with low dose-rate brachytherapy after trans- rectal ultrasound planning. In addition, 74 men implanted more recently after MRI planning. Results Median follow up of the 951 men was 7.9 years, with a range 2.0 – 16.3 years. Ten-year prostate specific antigen control was 95% for 551 low-risk patients and 82% for 400 intermediate-risk patients. 73 men developed biochemical failure (BF) and 17 men urethral stricture. Prostate specific membrane antigen PET-CT scanning performed on 34 men who underwent BF revealed that 27 (80%) had local recurrence, and of these, 25 (93%) had relapsed in the prostate base and/or seminal vesicles. A low prostate Dose 90 (≤90%) did not increase the risk of BF (P=0.127), but a small prostate volume (≤35 cc) increased both the risk of BF (P=0.02) and of urethral stricture (P=0.003). Men who developed urethral stricture were found to have twice as many seeds 10 mm below the prostate apex as men who did not, indicating that too low positioning of seed strands was usually responsible for this side effect. The increased risks associated with prostates ≤35 cc suggest that too low positioning occurs more often when the prostate is small. Three-Tesla MRI planning of 74 more recently implanted men permitted accurate definition of the prostate capsule and the position of the membranous urethra. Prostates ≤35 cc were found to be nearly always 35 mm in length prostate brachytherapy. Material and Methods

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Conclusion HDR-BRT represents an effective and safe solution for the treatment of NMSC, even in elderly population, with excellent clinical outcome and very low toxicity. More data with a longer follow-up are necessary. PV-0143 High-dose CT-guided interstitial brachytherapy of liver metastases in oligometastatic patients F. Walter 1 , S. Gerum 1 , M. Rottler 1 , C. Maihöfer 1 , J. Well 1 , L. Nierer 1 , M. Seidensticker 1 , R. Seidensticker 2 , T. Streitparth 2 , F. Streitparth 2 , J. Ricke 2 , C. Belka 1 , S. Corradini 1 1 Radiation Oncology, Department of Radiation Oncology LMU, Munich, Germany; 2 Radiology, Department of Radiology LMU, Munich, Germany Purpose or Objective Local treatment for liver oligometastases is a challenging issue. Aim of the present study is to report feasibility and outcome in this setting using high-dose CT-guided interstitial brachytherapy (BT). Material and Methods 36 patients (m:f 17:19) with a median age of 68 years (31- 88) who received high-dose brachytherapy on liver metastases between 01/18 and 06/18 were retrospectively analysed. Primary tumours were as follows: rectosigmoid carcinoma in 16 patients (pts), breast cancer in 4 pts, NET in 5 pts, gastric cancer in 3 pts and others (sarcoma, GIST, pancreatic cancer, colon cancer, prostate cancer). Results 18 out of 36 pts presented with a single hepatic lesion, 12 pts had two lesions and 6 pts had 3 or more lesions. Between 1 to 9 catheters were utilized for the procedure (1=7pts, 2=14pts, 3=5pts, >3=10pts). The median metastases diameter was 2.1cm (range 0.8-13.6cm) with a median volume of 2.4ccm (0.1-550.8ccm). The total liver volume ranged from 891-2761ccm (median 1402ccm). A medium dose of 19.7Gy was achieved in D100 (8.7- 26.1Gy), D98: 22.6Gy (9.6-33Gy), D95: 24.5Gy (10.1- 39.6Gy), and D90: 26.6Gy (10.6-49.7Gy). Liver dose exposure parameters were V5: 290.3ccm (43.7- 1792.2ccm), V10: 101.9ccm, and V15: 57.4ccm (8.4- 689.5ccm). Follow-up was available in 32 out of 36 pts and was between 28-144 days (median 86 days). In 29 pts local control was achieved, while in 4pts a local recurrence occurred. Conclusion CT-guided interstitial brachytherapy showed to be a safe and effective treatment approach for oligometastatic liver disease. Longer follow-up is needed to assess the role of this treatment modality in the oligometastatic setting as an alternative to other treatment approaches, including SBRT. PV-0144 Custom-made moulds plesiotherapy for non- melanoma skin cancer treatment M.Á. González Ruiz 1 , J.L. Muñoz García 2 , J. Quirós Rivero 2 1 Punta de Europa Hospital, Radiation Oncology, Algeciras, Spain; 2 Badajoz Universitary Hospital, Radiation Oncology, Badajoz, Spain Purpose or Objective To evaluate ourresults in terms of local disease free survival (LDFS), cosmesis and toxicity in patients (pts) with non-melanoma skin cancer (NMSC) treated with high-dose-