Abstract Book

ESTRO 37

S566

Conclusion Planner’s experience in SBRT prostate is correlated with dosimetric parameters and the modulation index MItotal. Complexity scores and dose distributions depend on specific dosimetric planning requests and replanning improves results in terms of homogeneity between centers whilst keeping the same level of plan complexity (MItotal): DVH sharing could aid in achieving better standardization. These results highlight the importance of training as well as the usefulness of a feedback strategy from multi-institutional comparisons. PO-1013 Using A Decision Board To Evaluate Patient’s Choice Of Either Ebrt Or Multicatheter APBI J. Tang 1 , V. Koh 1 , Y. Leong 1 , S. Buhari 2 1 National Cancer Institute Singapore, Radiation Oncology, Singapore, Singapore 2 National Cancer Institute Singapore, Surgery, Singapore, Singapore Purpose or Objective External Beam Radiotherapy(EBRT) over 42 days or Accelerated Partial Breast Irradiation(APBI) using the multicatheter approach over 5 days are suitable treatment options for early staged breast cancer women post breast conservation surgery. Our aim was to develop a visual aid to help patients select their treatment option and their reasons behind it. Material and Methods A decision board was designed listing the advantages and disadvantages of either modality as a visual aid. Each patient consult was standardized using the decision board as a tool for discussion. Patients were then asked which treatment was their preferred option and the reason/s for choosing that option. Results Of the 221 patients enrolled between August 2008 to August 2017, median age was 58, 70% were left sided tumors, 80% of patients spoke English, 86% were economically active at the time of diagnosis and none had ECOG ³3. Of the 188 patients choosing APBI, 100% of patients chose APBI for shorter fractionation and 92% chose APBI for better side effect profile especially for lower skin toxicity, cardiac toxicity and pulmonary toxicity. Of the 33 patients choosing EBRT, 100% chose EBRT for reasons of needle phobia and 85% for the cheaper cost. All reasons for fractionation choice were consistent with decision-board information, confirming validity. All patients were satisfied and happy to be involved in decision-making. Conclusion We have validated a decision board assisting patient choice of radiotherapy fractionation schedules either with APBI or EBRT for women with early staged breast cancer. All patients indicated that they were satisfied and happy to participate in the decision making process. PO-1014 Comparison of subjective and objective assessment of cosmetic outcome following breast brachytherapy T. Wadasadawala 1 , V. Parmar 2 , S. Sinha 3 , M. Mondal 3 , U. Jain 4 , S. Kannan 5 , R. Pathak 3 , R. Sarin 3 1 actrec-Tata Memorial Centre, Radiation Oncology, Navi Mumbai, India Poster: Brachytherapy: Breast

institutional studies can be challenging due to different Experience Level (EL). The aim of this work was to preliminary evaluate the role of a re-planning phase in a multi-institutional study for achieving similar plan quality results and for further benchmarking. Material and Methods 45 prostate SBRT plans from 9 centers were included. EL was ranked as 1 for 'no experience”, 2 for '<100 SBRT prostate cases planned” and 3 for '≥100 SBRT prostate cases planned”. Each center was provided with 5 anonymized CTs with pre-delineated volumes and was asked to create SBRT plans according to pre-set dose constraints. Dose prescription was 7Gyx5fr. The DVH text file and the RP_DICOM of each plan were used to extract dosimetric parameters, modulation indexes, and dynamic parameters from IMRT/VMAT plans. Results were summarized in a Spearman-correlation matrix and deemed correlated for R>0.50; statistical significance was set at p=0.01. In a 2 nd phase, planners were asked to re-plan the 5 th patient, based on the median DVHs of all partecipants, for improving target homogeneity and further sparing OAR doses. A Kruskal-Wallis rank test was performed to compare dosimetric and complexity parameters between the two series. Results In the 1 st phase, EL correlated with dosimetric parameters (see figure 1, with the correlogram showing significant positive (blue) and negative (red) correlations). The volume of rectum receiving > 32 Gy (V32 Gy Rectum, 9.1±4.4%) showed strong correlation with EL (p<0.0001): the higher the planner had experience level, the lower the doses to OARs were. When comparing only VMAT plans, the total Modulation Index (MItotal=0.70±0.21) was strongly correlated (p<0.001) with EL: the higher the experience level was, the lower the degree of plan complexity was reached. In the re-planning phase, the Kruskal-Wallis test showed significant differences in the doses to the rectum between both phases; no significant differences were found in the dynamic parameters of the plan and in the modulation indexes (see figure 2).