ESTRO 37 Abstract book

one. Although the fourth protocol allows decreasing PTV2, it is not recommended as a protocol to be used to decrease PTV1. The best control of changes connecting to the area covered by PTV1 provides the third type of protocol. Conclusion The choice of the appropriate protocol should be validated in the context of (i) institutional practice regarding patient set-up procedure and its time consumption, (ii) acceptable balance between the amount of the dose delivered to the organ at risk and the additional imaging dose and (iii) patient anatomical conditions. EP-2387 Retrospective analysis of offline chosen plan V's online chosen plan for gynaecological patients. C. Duncanson 1 , A. Sadozye 1 , R. Harrand 1 1 Beatson West of Scotland Cancer Centre, Radiotherapy, Glasgow, United Kingdom Purpose or Objective A retrospective analysis of inter-observer chosen plan-of- the-day (PoD) compared with actual treated PoD for cervical and endometrial cancer patients. Aim is to determine the level of concordance between specialist gynaecological radiographer chosen offline plan compared with real-time online plan selected by appropriately trained treatment radiographers, to evaluate if there is a need for further in-house training to improve confidence levels during plan selection. Material and Methods A total of 20 patients planned and treated with adaptive planning margins for cervix or endometrial cancers were reviewed retrospectively by the specialist gynaecological radiographer. Daily online cone beam computed tomography scans (CBCT’s) were captured for each patient. A total of 500 CBCT images were reviewed offline. The treatment plan selected for each fraction was recorded. There was a library of 2 plans available, the standard clinical protocol plan and the plan with additional margins to account for OAR movement and target motion (adaptive plan). The specialist radiographer then reviewed the CBCT’s and made an independent choice between the two PTV’s based on PTV coverage, nodal coverage, bowel dose, bladder filling and rectal volume. This was also tabled and compared with the online selected plan and the results analysed accordingly. Results Of the 20 patients within the sample, 9 patients were post-op endometrial cancer and 11 patients were intact cervical cancer patients. The range of concordance between all patients in both groups was 58.9% - 100%. There was an average discrepancy rate of 7.8% (92.2% concordance) within the post op group, however in the intact cervical group this was higher with an average 9% discrepancy rate (81% concordance). The overall concordance rate was high at 91.23%. One patient in the post-op group had a high discrepancy rate due to issues with bladder and bowel volumes which brought the average down substantially. Conclusion High overall concordance rates were observed between offline and online plan selections. Slightly lower concordance was noted within the intact cervical cancer patient group as a result of greater organ motion to uterus motion based on bladder filling and rectal emptying variability. More regular in-house CPD sessions could be offered to assist staff in reviewing CBCT in Electronic Poster: RTT track: Motion management and adaptive strategies

particular using any problematic patients previously treated to allow for greater education and confidence when selecting PoD for gynaecology cancer patients. EP-2388 Use of helical tomotherapy for local treatment in metastatic breast cancer: single center experience L. Thery 1 , M. Amessis 1 , C. Adrien 1 , A. Fourquet 1 , Y.M. Kirova 1 1 Institut Curie, Radiotherapy, Paris, France Purpose or Objective Helical tomotherapy (HT) improves target coverage and dose homogeneity and allows sparing of the organs at risk (OAR) compared to standard techniques. For patients with metastatic breast cancer (MBC) heavily pretreated, reduce the overall burden of radiotherapy is a major challenge. This study assesses the impact of HT in terms of acute and late toxicity and the survival in metastatic breast cancer. Material and Methods We retrospectively reviewed data of 57 patients (pts) with metastatic breast cancer who were treated by HT between 2008 and 2015. Irradiated volumes included breast+/- boost, or chest wall, axillary lymph nodes (LN) +/- internal mammary nodes (IMN) +/- mediastinum LN (in case of involvement). All patients received normo fractionated radiotherapy, with or without concurrent systemic treatment. The median survival outcomes were estimated with the Kaplan-Meier methods. All toxicities were described using the Common Toxicity Criteria for Adverse Events v4. Results Fifty-seven pts with stage IV have been studied. Median age was 60 years (range 28-77). The median follow-up was 41 months (range 10.8-95.8). Three (4,5%) pts presented with chronic respiratory disease, 19 (28,7%) pts were smokers. The coverage of target volumes (PTV) was as follows : breast 51,8 Gy ; simultaneous integrated boost 63 Gy ; chest wall 50 Gy ; PTV lymph nodes 50,4 Gy ; mediastinum 50 Gy. Systemic treatments were administered concurrently with HT in 95% of cases. Hormonal therapy (45%) was the most commonly used concurrent systemic agent followed by the association Trastuzumab and Pertuzumab (19.6%) and the oral chemotherapy Cyclophosphamide (10.5%). Most pts experienced grade 1 and 2 skin toxicity, as follows: grade grade 1=30 (52.6%), grade 2=11 (19.3%). Only 2 pts experienced grade 3 skin toxicity (concurrent 5 Fluorouracile and Vinorelbine-HT) and their irradiation was interrupted for local care. There were 42 pts (73.7%) with grade 0 esophagitis, 11 pts (19.3%) with grade 1 and 4 pts (7%) presented with grade 2 esophageal toxicity. One patient receiving concurrent treatment with Trastuzumab and Pertuzumab had a decreased left ventricular ejection fraction (by 14% compared to the initial value). There was no case with grade 1-2 pulmonary fibrosis. No cardiac or lung late toxicity was observed. On 9 pts with tumor involving skin, HT led to significant clinical improvement in almost 89%. The median survival was 37.5 months [95% CI, 32.6 to 42.3]. Conclusion This retrospective study suggests that the use of HT to irradiate complex volumes in patients with MBC is well tolerated and is feasible in association with systemic treatments, thus allowing to benefit from its more homogeneous volume coverage that standard irradiation. Its low side effects and its efficacy seem to be an asset for the future. Larger prospective studies with longer follow-up are needed to confirm these results.