ESTRO 38 Abstract book

S701 ESTRO 38

K. Ono 1 , T. Taniguchi 1 , K. Shiraki 1 , Y. Itou 1 , O. Tanaka 1 1 Asahi University Hospital, Department of Radiation Oncology, Gifu, Japan Purpose or Objective To reduce the Heart`s dose for patients undergoing postoperative radiotherapy for left-sided breast cancer is critical for the heart disorder. Deep inspiration breath hold and intensity modulated radiation therapy (IMRT) are reported as methods for reducing the cardiac dose, especially for the left anterior descending artery (LAD). We compared the radiation methods of various degrees and examined the details of the difference between static IMRT and volumetric modulated arc therapy (VMAT). Material and Methods Overall, 20 patients underwent postoperative radiotherapy for left-sided breast cancer from July 2016 to June 2018 at our institute. We conducted the following five treatment plans: 2 field-static IMRT (2 F-S-IMRT), 4 field-static IMRT (4 F-S-IMRT), 40 degrees dual partial arc VMAT (40d VMAT), 80 degrees dual partial arc VMAT (80d VMAT), and 210 degrees partial VMAT (210p VMAT). The prescription dose was 50 Gy/25 fractions for the planning target volume (PTV) in all treatment plans. The dosimetric calculation was optimized to achieve a coverage of 50 Gy prescribed for 95% of PTV by inverse treatment planning using the Monte Carlo algorithm. Each of the five treatment regimens was analyzed by the dose volume histogram(DVH), and the multiple comparison test was performed. The evaluation items were compared on Heart's V 10 (coverage of 10% of the volume of the heart), LAD's V 10, PTV's D95, and homogeneity index (HI). Results The coverage of 40d VMAT for the prescribed dose of PTV’s D95 was significantly lower than that of the other treatment plans. The D95 of the breast of PTV was approximately 46 Gy. HI was also high, and uniformity within PTV was decreased. For the other treatment plans, D95 showed high PTV coverage, i.e., 48 Gy or higher. 4F- S-IMRT became the best dose distribution (D95 = 49.2 Gy, HI = 1.08 and PTV). As for the dose of Heart and LAD, 2 F- S-IMRT, 40 dV MAT, 80 dV MAT was highly effective in reducing the dose. As for the OAR dose, 2F-S-IMRT was the highest in a reduction effect for the Heart and LAD (the value was V10 = 9.3% of the Heart, V10 = 45.3% of LAD). Table Dose comparison of the PTV, Heart and LAD in the Five plans. Conclusion 2 F-S-IMRT and 40d VMAT had adventage for lowering the dose of OAR,because the number of fields and the irradiation range angle are small. 4F-S-IMRT and 80d VMAT increase an X-ray beam from multiple directions, which ensured not only sufficient coverage of PTV but also reduced the heart`s dose. In these methods, dispersion of D95 in PTV may be reduced. The shape of the mammary gland differs in each patient; these methods ensure the possibility of administering optimum dose prescription and thereby have clinical applications. EP-1279 M1 neck lymph node positive without distant metastasis in breast cancer: comparison with stage IIIC J.S. KIim 1 , K. Kim 2 , K.H. Shin 1 , J.H. Kim 1 , S.S. Kim 3 , T.H. Kim 4 , Y.B. Kim 5 , W. Park 6 , J.H. Kim 7 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of ; 2 Ewha Womans University College of Medicine, Department of Radiation Oncology, Seoul, Korea Republic of ; 3 Asan Medical Center, Department of Radiation Oncology, Seoul, Korea Republic of ; 4 National Cancer Center,

HF-WBI was similar ( k =0.3465, wk =0.4514). The agreement between IE and CE of A using photographs before HF-WBI was poor ( k =0.1306, wk =0.2158), and that using photographs after HF-WBI was similar ( k =0.1180, Although the agreement between IE and CE was poor both before and after HF-WBI, the inter-observer variability of CE was smaller than the intra-observer variability of PE. CE using BCCT. core was considered a reproducible evaluation method when cosmetic changes of breasts that had received HF-WBI were evaluated comparing the photographic appearances before and after treatment. EP-1277 Locoregionally recurrent breast cancer treated with postoperative or salvage radiotherapy B.H. Kim 1 , K.H. Shin 2 , E.K. Chie 2 , J.H. Kim 2 , K. Kim 3 , S. Kim 1 1 SMG-Seoul National University Boramae Medical Center, Radiation Oncology, Seoul, Korea Republic of ; 2 Seoul National University College of Medicine, Radiation Oncology, Seoul, Korea Republic of ; 3 Ewha Womans University College of Medicine, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective The purpose of this study was to investigate the treatment patterns and outcomes of patients receiving radiotherapy (RT) for isolated locoregional recurrence (ILRR) of breast cancer. Material and Methods We retrospectively analyzed the medical records of 125 patients who were diagnosed with ILRR after initial curative resection (mastectomy or breast-conserving surgery) and underwent RT from 2006 to 2016 at two institutions. The median time from initial operation to ILRR was 38 months. After ILRR, 96 (77%) patients underwent curative resection followed by postoperative RT and 29 (23%) underwent salvage RT. Ninety-eight (78%) patients received systemic chemotherapy. Median RT dose was 51.0 Gy (range: 18.0-70.4). Results The sites of recurrences were classified as follows: local in 42 (34%) patients, regional lymph nodes in 64 (51%), and combined local and regional sites in 19 (15%). Twenty- eight (22%) patients had received RT for primary breast cancer, but only 10 (8%) underwent re-irradiation. The patterns of treatment were very heterogeneous according to the patient and disease presenting features, and partial breast irradiation or hyperthermia was not performed. Overall, 5-year locoregional progression-free survival, distant metastasis-free survival, progression-free survival (PFS), and post-recurrence overall survival (OS) were 78.4%, 59.0%, 55.0%, and 69.7%, respectively. On multivariate analysis, initial pN0-1 stage, disease-free interval (≥ 36 months), and curative resection for recurrent disease were found to be independently associated with better PFS and OS. When we divided patients into four groups based on the number of prognostic factors, pairwise significant differences in PFS and OS were found. Grade 3 dermatitis and grade 2 lymphedema were observed in 2 (1.6%) and 6 (4.8%) patients, respectively. Conclusion Most patients with ILRR of breast cancer referred for RT were radiation-naive and re-irradiation was not actively carried out. RT following curative resection could achieve favorable PFS in these potentially salvageable patients without causing severe toxicity. Initial pN stage, disease- free interval, and curative resection for recurrent disease were important prognosticators. EP-1278 Effect of heart`s dose reduction by IMRT in postoperative radiotherapy for left-sided breast cancer wk =0.2240). Conclusion