ESTRO 2020 Abstract Book

S514 ESTRO 2020

Oncology, Namdong-gu- Incheon, Korea Republic of ; 2 Gachon University Gil Medical Center, Dermatology, Namdong-gu- Incheon, Korea Republic of Purpose or Objective Various topical agents have been used to manage radiation dermatitis during radiation therapy. No topical agent has proven to be better than any other. This work aims to validate the efficacy of a film-forming silicone gel (StrataXRT ® ) for patients receiving whole breast radiotherapy. Material and Methods A single institutional, open-label, randomized, pilot study was performed in 49 breast cancer patients receiving radiotherapy after breast conserving surgery. Patients were randomized to use a film-forming silicone gel (StrataXRT group) or a moisturizing cream (X-derm ® group). The severity of radiation dermatitis was graded using physiological skin parameters (erythema index, melanin index, and trans-epidermal water loss; TEWL), provider-assessed visual rating scales (CSSP, RTOG, and CTCAE scales) and patient-reported symptoms (dryness, itchiness, burning sensation, and pain). Changes in these parameters from baseline to 4 weeks post-radiotherapy were evaluated every two weeks. Two-way repeated- measures ANOVA with Greenhouse-Geisser correction followed by Bonferroni's post hoc test was used to analyze the difference of changes in the severity of radiation dermatitis. Results Two-way repeated-measures ANOVA revealed different patterns of changes in erythema index (F=3.609, p =0.008) and melanin index (F=3.475, p =0.015). When compared with X-derm group, the StrataXRT group showed significant reductions in erythema index at the end of radiotherapy ( p <0.001) and melanin index at two weeks post- radiotherapy ( p =0.006). There were no significant differences between groups with respect to TEWL, clinician-assessed visual rating scales, and self-reporting questionnaires. Conclusion The use of the film-forming silicone gel appears to have a positive effect toward reducing radiation dermatitis compared to that of a moisturizing cream. The results of this study will support the feasibility of conducting a larger randomized control trial. PO-0965 Cardiac dosimetry with or without ABC in left breast cancer irradiation: Single institute experience V. Pareek 1 , R. Bhalavat 2 , M. Chandra 2 , P. Bauskar 2 , N. Kumar 2 , E. Kotilingala 2 , P.L. Iyer 2 1 National Cancer Institute- AIIMS, Radiation Oncology, New Delhi, India ; 2 Jupiter Lifelines Hospital, Radiation Oncology, Thane, India Purpose or Objective Cardiac toxicity is a major concern for left breast tangential field irradiation. The left ventricle and left anterior descending (LAD) artery are suggested to be radiosensitive and radiation to these structures leads to late cardiotoxicity. Moderate deep inspiration breath hold (mDIBH) during radiation treatment delivery helps in reducing the cardiac dose. This study compares dosimetric parameters of heart with and without active breath coordinator (ABC) mDIBH during tangential field breast cancer radiation. Material and Methods In our dosimetric comparative study, Thirty consecutive patients with left-sided breast cancer who underwent breast-conserving surgery and adjuvant tangential field and radiotherapy with ABC mDIBH between July 2018 and September 2019 in our center were analyzed in this study. The ABC device was used for respiratory control and patients who could hold their breath for 20–30 s were considered for radiation with ABC mDIBH. Simulation scans

with IBTR on MVA. Cosmesis was good-to-excellent in 89.7% after APBI. Conclusion For women under 50 years of age, APBI results in excellent long-term disease control. Cosmetic outcomes are good- to-excellent in most patients. Our results suggest that APBI is a reasonable alternative to WBI in select women under 50, and further efforts to enroll this poorly represented group on prospective trials should be prioritized. PO-0963 Impact of regional nodal Irradiation on lung dose in hypofractionated radiation of breast cancer M. Bohli 1 , Z. Fessi 1 , A. Hamdoun 1 , J. Yahyaoui 1 , R. Moujahed 1 , L. Kochbati 1 1 Abderrahman Mami Hospital, radiation oncology, Ariana, Tunisia Purpose or Objective Ipsilateral lung is one of the main organ at risk in breast radiation. The proximity of sub-volumes (level 3 and Level 4 regional lymph nodes) to the lung is an important determinant of radiation pneumonitis risk. Experimental models showed that the lung apex was more radioresistant than the base due to non-uniform distribution of alveoli throughout the lung. Our purpose was to study the contribution of supra and sub clavicular (periclavicular) field on the lung irradiation and to analyze factors that influence the mean dose (D_mean) to the lung. Material and Methods During the year 2018, 78 patients were treated with adjuvant loco-regional hypofractionnated radiation for breast cancer. Conservative surgery or modified radical mastectomy were included. A dose regimen of 40 Gy/15 fractions is used with a tumor bed boost of 13.35Gy/5 fractions after conservative surgery. All treatment plans were mono-isocentric. Dosimetric data for ipsilateral lung, with and without periclavicular field were recorded (D_mean, volume receiving 4Gy (V4Gy), V8Gy, V10Gy, V12Gy, V16Gy and V20Gy). We assessed correlation between dosimetry plans according to periclavicular radiation, and then we evaluated factors that influence D_mean that are lung volume (cm 3 ), beam energy (6MV, 18MV, 6+18MV), chest wall separation(cm), distance to the lung apex(cm), depth of periclavicular volume (cm) and size of periclavicular field(cm) Results Mean D_mean, V4(Gy), V8, V10, V12, V16 and V20 for plans with tangential and periclavicular fields were 10Gy, 43%, 34%, 31%, 29%, 25% and 23% respectively versus 6Gy, 27%, 21%,19%, 18%, 16% and 14% respectively for plans with tangential fields without periclavicular fields. The contribution of periclavicular fields was statistically significant in all cases (p< 0.0001). A significant correlation was found between D_mean and length of periclavicular field (p=0.033), distance to the lung apex (p=0.001) and chest wall separation (0.001). There was no correlation with width of periclavicular field (p=0.263), lung volume (p=0.129), depth of periclavicular field (0.093), and beam energy (p=0.443). Conclusion Periclavicular field increased significantly all ipsilateral lung dosimetric parameters (p<0.001). It contributed up to 40% of D-mean (about third of the dose). Factors affecting D-mean were length of periclavicular field, distance to the lung apex and chest wall separation. Therefore, an accurate contouring of level 3 and 4 areas according to ESTRO guidelines is mandatory to ovoid large fields and exceeded dose to the lung. PO-0964 Reducing radiation dermatitis using a film- forming silicone gel: a pilot randomized controlled trial K. Sung 1 , S. Ahn 1 , H.J. Kim 1 , Y.E. Choi 1 , Y.K. Lee 1 , J.S. Kim 2 , S.K. Lee 2 , J. Roh 2 1 Gachon University Gil Medical Center, Radiation