ESTRO 36 Abstract Book

S632 ESTRO 36 2017 _______________________________________________________________________________________________

S.H. Liu 1 , Y.C. Huang 2 , Y.J. Chen 1 1 Mackay Memorial Hospital, Department of Radiation Oncology, Taipei, Taiwan 2 Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan Purpose or Objective For patients with 4 or more lymph nodes involvement, regional nodal irradiation (RNI) is associated with increased locoregional control and overall survival (OS). The main radiotherapy (RT) volume for RNI includes axillary, supraclavicular, and/or internal mammary nodes. However, whether the posterior supraclavicular area and the posterior triangle of the neck (PSPT) should be included in RNI remains unclear. The object of this study was to retrospectively review our clinical experience of RNI to PSPT or not in N2-3 breast cancer patients as a reference for target delineation. Material and Methods Patients with N2-3 breast cancer who received definitive surgery and/or neoadjuvant/adjuvant therapy during 2006–2013 were reviewed. The delivery of adjuvant RT and the coverage for RNI were at the discretion of treating physicians. To ensure precise delineation and dosimetry, only patients treated using the technique of intensity- modulated radiotherapy (IMRT) to regional nodal area were enrolled. The patterns of recurrence including the PSPT region were examined. The locoregional control rate (LCR), distant metastasis-free rate (DMFR), disease-free survival (DFS), and OS were analyzed using Kaplan-Meier method, and survival estimates were obtained with log- rank test and the Cox proportional hazard model. Results Of 256 N2-N3 breast cancer patients who were diagnosed and received operation in a medical center, 184 cases were eligible for the study. Among these women, 62 received RNI according to the recommended volume by RTOG consensus (RC group), 57 had additional volumes of PSPT (RC+PSPT group), and 65 did not have adjuvant RT (NRT group). Median follow-up was 62.8 months for the entire cohort. There was higher LCR (p=0.006, 90.8% vs. 78.5% at 5 years) and OS (p=0.007, 82.7% vs. 64.8% at 5 years) for the patients with adjuvant RT (RC and RC+PSPT) compared to those without RT (NRT). No difference in DMFR (p=0.508, 69.6% vs. 63.4% at 5 years) and DFS (p=0.243, 68.2% vs. 69.2% at 5 years) were noted. Among women with adjuvant RT, there was no statistical difference between RC and RC+PSPT groups (LCR: p=0.693, 93.1% vs. 89.9% at 5 years; DMFR: p=0.501, 66.2% vs. 73.9% at 5 years; DFS: p=0.606, 66.2% vs. 71.6% at 5 years; OS: p=0.548, 83.5% vs. 83.5% at 5 years). In details, locoregional recurrence was found in 4 (6.5%), 6 (10.5%), and 17 (26.2%) patients in the RC, RC+PSPT and NRT group, respectively. Among these patients, no PSPT recurrence was noted in RC+PSPT group, whereas there were 2 (50%) in the RC group and 11 (64.5%) in the NRT group. Conclusion Adjuvant RNI significantly increased LRC and OS for N2-N3 breast cancer patients. Local recurrence specifically noted in PSPT might be diminished by additional inclusion in the regional nodal irradiation volumes. This impact may not translate to the changes in LCR, DMFS, DFS, and OS in our experience. Further prospective investigation is needed to validate these results with exclusion of possible selection bias. EP-1175 Impact of body-mass index on setup displacement in patients with breast cancer Y.C. Tsai 1 , C.Y. Chen 2 , J.T. Tsai 1 1 Taipei Medical University-Shuang Ho Hospital, radiation oncology, New Taipei City, Taiwan 2 Wan Fang Hospital- Taipei Medical University, Radiation oncology, Taipei, Taiwan

To determine the impact of body-mass indexfactors (BMIF) on daily setup variations for patients with breast cancer treated with adjuvant radiotherapy with daily image guidance.before radiotherapy and changes duringradiotherapy on the magnitude of setup displacement in patients with breast cancer. Material and Methods The clinical data of 117 patients with breast cancer was analyzed using the alignment data from daily on-lineon- board imaging from image-guided radiotherapy between 2013 and 2015. All patients received cone beam computed tomography(CBCT) at the first 5th fraction, then once per week at least. BMFs included body weight, body height, and thecircumference and bilateral thickness of the neckThe shifts of each fraction were collected in superior- inferior (SI), anterior-posterior (AP), and medial-lateral (ML)directions respectively, and the absolute distant of shifts was also calculated. The shifts of patients were grouped by factors of BMI, body weight, height, age, operation method and acute toxicities respectively. For grouping of BMI,body weight and height, the median values were used as cut off. The impact of factors as assessed by compare the shifts using independent t-test within each groups. Results Median BMI was 24.3, and median body weight was 59kg. A higher body weight before radiotherapy correlated with a greater shift in ML(p =0.0088 ), and SI(p = 0.0004) direction. A larger BMI( ≧ 24.3) was associated with a greater shift in SI (p = 0.0005) direction. Comparsion of patients undergoing breast-conserving surgery(BCS) and modified radical mastectomy(MRM), BCS group was associated with a larger shift in SI and ML(p=0.028 and p=0.0051, respectively). Conclusion Larger body weight( ≧ 59kg, larger BMI( ≧ 24.3) and BCS may be a significant risk factor for daily shifts. EP-1176 Helical tomotherapy in chest wall/breast and draining node irradiation after breast cancer surgery V. Lancellotta 1 , M. Iacco 1 , S. Chierchini 1 , E. Perrucci 1 , I. Palumbo 1 , L. Falcinelli 1 , S. Saccia 1 , S. Nucciarelli 1 , A. Milletti 1 , C. Aristei 1 1 Ospedale Santa Maria della Misericordia, Radiation Oncology, Perugia, Italy Purpose or Objective Three dimensional conformal radiotherapy (3DCRT) to the chest wall/breast and draining nodes has long been standard treatment for patients at high-risk of relapse after mastectomy or conserving surgery (BCS). Given the complex target shape, other radiotherapy techniques such as intensity modulated RT (IMRT), volumetric modulated arc therapy (VMAT), helical (HT) or direct (DT) tomotherapy were developed. The present study evaluated the toxicity of HT for treating the chest wall or breast plus level III and IV lymph nodes after mastectomy or BCS. Material and Methods From January 2013 to August 2016, 43 consecutive patients with breast cancer underwent helical tomotherapy . Table 1 reports their demographics and clinical details. Computed tomography (CT) scans without contrast medium were acquired with patients supported by breast board in the treatment position. CT data were acquired with 2.5 mm slice thickness and were transmitted to the Pinnacle 3 TPS V9.8. One radiation oncologist contoured the clinical target volume (CTV) i.e. chest wall or breast, level III and IV lymph nodes and organs at risk. The chest wall was not expanded to obtain the planning target volume (PTV); the breast and nodes were expanded 0.5 cm in all directions to obtain the PTV breast and PTV ln. Dose prescription was 50 Gy to the PTVs in 25 fractions. In 7 patients treated with BCS a simultaneous integrated boost (SIB) was delivered to the

Purpose or Objective