ESTRO 37 Abstract book

S1223

ESTRO 37

SAVI.The region of interest to be evaluated is a PTV = "PTV_EVAL" for dose assessment excluding the SAVI catheter, adding 2 mm from the skin side and 0 mm from the chest wall, adding a 3-dimensional margin of 10 mm to the SAVI catheter, Skin = "SKIN", chest wall = "CHEST WALL". Evaluation items and dose constraints were evaluated on the degree of achievement of the dose constraint, with V 90% ≧ 90%, V 150% ≤ 50 ml, V 200% ≤ 20 ml at "PTV EVAL", and D 1 ml ≤ 110% for "SKIN" and "CHEST WALL" . Results Dose constraints were achieved in 37 cases in 42 cases, but 5 cases failed to satisfy the constraints. The degree of achievement was "PTV_EVAL" V 90%: 100%, V 150%: 100%, V 200%: 92.9%, "SKIN" D 1 cm 3 : 100%, "CHEST WALL" D 1 cm 3 : 97.6%. Dose constraints were achievable for "PTV_EVAL" V 90%, V 150%, "SKIN" D 1 cm 3 in all cases. In cases where the constraint could not be met, proximity of the applicator to the risk organs was observed. Conclusion From this examination, deviations in dose constraints were observed in several cases, but it is suggested that the achievement of dose constraint in SAVI was good in most cases. EP-2213 A subcutaneous spacer injection for skin protection during breast brachytherapy – a pilot study. G.M. Struik 1 , J.P. Pignol 2 , A. Ghandi 3 , I.K.K. Kolkman- Deurloo 4 , E. Birnie 5 , T.M.A.L. Klem 1 1 Franciscus Gasthuis en Vlietland, Surgery, Rotterdam, The Netherlands 2 Erasmus Medical Center- Cancer Institute, Radiation Oncology, Rotterdam, The Netherlands 3 Franciscus Gasthuis en Vlietland, Radiology, Rotterdam, The Netherlands 4 Erasmus Medical Center- Cancer Institute, Radiation Oncology - Physics, Rotterdam, The Netherlands 5 Franciscus Gasthuis en Vlietland, Statistics and Education, Rotterdam, The Netherlands Purpose or Objective Partial breast irradiation following breast conserving surgery has shown equal effectiveness as whole breast irradiation in a selected group of early stage breast cancer patients. Brachytherapy is the most frequently used technique with the longest experience and highest level of evidence. Main side effect of all forms of breast brachytherapy is skin toxicity, with dose to the skin as main risk factor. The use of spacers was previously investigated in prostate cancer patients to separate the rectum wall. We hypothesize that injection of an inert/biodegradable spacer between the dermis and the most superficial layer of the planned target volume (PTV) removes the skin from the high dose volume in breast brachytherapy, and this would result in a significant reduction of moist desquamation and eventually telangiectasia. Purpose of this pilot study is to evaluate the concept of a subcutaneous spacer injection in the breast and predict the dosimetry consequences, using PBSI planning as an example. Material and Methods A pilot study of an ultrasound guided spacer injection was performed on mastectomy specimen. Two products were tested: hyaluronic acid (HA) (“Barrigel”) and iodined PolyEthyleneGlycol (PEG)(“TraceIT”). Success of the intervention was defined as creating a thickness of ≥5mm subcutaneously in a skin area with a 20mm radius. Possibility of hydrodissection was recorded and ease of use was measured with the System Usability Scale (SUS). CT-scans were made pre- and post-injection. Brachytherapy planning was performed on a simulated Clinical Target Volume (CTV) and dosimetry was calculated with and without spacer. V 100 , V 200 were calculated as quality assurance of the planning. Dose to small volumes (D 0.2cc and D 0.05cc ) and the occurrence of

Electronic Poster: Brachytherapy: Breast

EP-2211 13 years of APBI multicatheter interstitial brachytherapy in patients not suitable Radiotherapy L. Trigo 1 , J. Silva 2 , P. Fernandes 1 , C. Dias 2 , A. Aguiar 2 1 Instituto Português de Oncologia do Porto Francisco Gentil- EPE, Brachytherapy Department, Porto, Portugal 2 Instituto Português de Oncologia do Porto Francisco Gentil- EPE, Radiotherapy Department, Porto, Portugal Purpose or Objective The increasing use of APBI after breast-conserving surgery has emerged from the need to provide shorter overall treatment time for patients with co-morbidities unsuitable for whole breast external beam radiotherapy (EBRT), patients living far away from radiotherapy centres as well as social and economic problems, pose financial and logistical hardships on patients and medical systems. This technique is now considered a viable treatment option outside clinical trials, due to the recent of the clinical trial of GEC-ESTRO (Grouped European de Curiethérapie-European Society for Radiotherapy and Oncology).We analysed the results of patients treated with Accelerated Partial Breast Irradiation (APBI) with multicatheter interstitial brachytherapy over 13 years of practice. Material and Methods We retrospectively analysed 109 patients treated from 2003 to 2016 with APBI at a single institution, and collected data regarding tumour, treatment and patient- related features. APBI consisted either in placing metal needles or flexible plastic catheters, using a template- based technique. Dose prescriptions ranged from 40 to 50 Gy (0,8 to 1 Gy/h) with PDR (Pulse Dose Rate) and 32 Gy in 8 fractions with HDR (High Dose Rate). All patients were then classified as “suitable”, “cautionary” and “unsuitable” as well as “low risk”, “intermediate risk” and “high risk” according to the CS of GEC-ESTRO and ASTRO. The outcome in terms of ipsilateral local recurrence, regional node relapse and distant metastases was assessed. Results Median follow-up time was 59 months. 74 patients undergone HDR and 35 a PDR technique. No loco-regional relapses were documented. 1 patient developed brain metastasis. Six patients did not meet the necessary criteria to be classified. Conclusion This study supports the evidence that APBI using multicatheter brachytherapy are treated in short time, presents excellent local control and overall survival being safe and effective method of delivering radiotherapy to breast cancer patients. EP-2212 Investigation of DVH Parameters for Accelerated Partial Breast Irradiation Using SAVI in Japan K. Miyaura 1 , H. Shinjoh 1 , T. Kubo 1 , A. Niiya 1 , R. Kobayashi 1 , M. Kato 1 , Y. Ozawa 1 , N. Okabe 1 , K. Murakami 1 , M. Morota 1 , Y. Kagami 1 1 Showa University, Radiation oncology, Tokyo, Japan Purpose or Objective We started accelerated partial breast irradiation (APBI) after breast conservation surgery using SAVI (Strut Adjusted Volume Implant) from March 2014, and 42 cases were treated until the end of May 2017. We investigated the dose constraint achievement of the region of interest from the DVH parameter in the case that was performed. Material and Methods The DVH parameter was calculated for the initial treatment plan of 42 patients who underwent APBI by