ESTRO 2022 - Abstract Book

S1026

Abstract book

ESTRO 2022

P.E. MURINA 1 , D. Angel 2 , O. Muriano 2 , A. Giraudo 2 , A. Villegas 2 , M. Galletto 2 , S. Zunino 2

1 Instituto Zunino, Radiotherapy, Córdoba , Argentina; 2 Instituto Zunino, Radiotherapy, Córdoba, Argentina

Purpose or Objective Between August 2016 and August 2020, 50 patients (52 tumors) were treated, 2 patients with bilateral breast, average age 83.9 years (70-91) with a diagnosis of Tis, T1 and T2 breast cancer, all N0, M0; histology: invasive ductal / lobular carcinoma or ductal carcinoma in situ, irradiated in a single institution. Immobilization with vacuum bag and simulation with SIEMENS Spirit dedicated institutional tomograph and irradiated with Novalis accelerator (Varian BrainLab). Positioning both arms up from the head. ExacTrac image-guided intensity modulated technique (IMRT + IGRT) was used. Total breast volume was irradiated without boost. The prescription dose was 28 Gy (25-29), EQD2 48.9 Gy (42.5-51.0), BED 81.3 (66.6-85.1). Toxicity was evaluated in person or by telephone survey. Materials and Methods Between August 2016 and August 2020, 50 patients (52 tumors) were treated, 2 patients with bilateral breast, average age 83.9 years (70-91) with a diagnosis of Tis, T1 and T2 breast cancer, all N0, M0; histology: invasive ductal / lobular carcinoma or ductal carcinoma in situ, irradiated in a single institution. Immobilization with vacuum bag and simulation with SIEMENS Spirit dedicated institutional tomograph and irradiated with Novalis accelerator (Varian BrainLab). Positioning both arms up from the head. ExacTrac image-guided intensity modulated technique (IMRT + IGRT) was used. Total breast volume was irradiated without boost. The prescription dose was 28 Gy (25-29), EQD2 48.9 Gy (42.5-51.0), BED 81.3 (66.6-85.1). Toxicity was evaluated in person or by telephone survey. Results 50 patients (2 patients with bilateral SBRT) in total, 52 volumes irradiated and controlled. Mean follow-up 30 months (8-57 months), 26 patients left breast, 26 right breast. All with quadrantectomy + - sentinel node, 49 luminal A patients and 1 triple-negative patient and 2 luminal B patients. Hormonal treatment managed at the discretion of the oncologist. During treatment 1 patient with G2 epidermitis, 17 G1 epidermitis and 32 (56%) without toxicity. At 2-3 weeks, 2 epidermitis G2 and 12 G1; 1 edema G2 and 4 G1; 1 mild pain. At more than 8 months, 1 patient G2 edema and 1 G1; 1 fibrosis G2, 6 G1; 1 hyperchromia G1 patient, 2 mild pain patients, and 38 patients (76%) without toxicity. All patients expressed comfort and adherence to treatment At 2-3 years 3/26 patients presented scattered telangiectasias 1/50 presented lymph node relapse (Triple negative), the rest free of disease Conclusion Despite the short follow-up time, the low toxicity suggests that this ultra-short treatment is feasible for women older than 70 years with low risk factors and could be considered for this age group for reasons of comfort and distance. 1 Teikyo University, Department of Radiology, Tokyo, Japan; 2 Teikyo University, Central Radiology Division, Tokyo, Japan; 3 Teikyo University, Graduate School of Medical care and technology, Tokyo, Japan; 4 Teikyo University, Nuclear Medicine, Tokyo, Japan Purpose or Objective Radiation treatment planning (RTP) is based on the clinical stage at diagnosis and the pathological stage after surgery in postoperative radiotherapy for patients with breast cancer who undergo neoadjuvant chemotherapy (NAC). However, adopting initial PET-CT images for RTP is challenging because of image registration inconsistency due to different acquisition conditions. We compared relevant clinical parameters in between patients who underwent PET-CT under the same conditions as those at the RTP (group A) and those who did not (group B). Materials and Methods Dose-volume histogram parameters of targets and organs at risk were evaluated for thirty consecutive cases from May 2019 to November 2020, in which PET-CT imaging was performed under the same postural conditions as for radiotherapy (flat panel on the patient back and both upper arms raised, group A), and thirty consecutive cases before then (group B). Regions of interests were generally set according to the RTOG contouring guideline, with appropriate individual modifications. All primary tumors and lymph node metastases considered to be positive at initial PET-CT before NAC were included in the target with ANACONDA deformable image registration technique. Prescribed doses were 50 Gy in 25 fractions or 42.56 Gy in 16 fractions. Results Both groups were well-balanced in age, BMI, laterality, clinical/pathological T stages, and pathological N stage without significant difference in clinical N stage. Among the targets, favorable coverages in CTVs and PTVs were observed in the group A, and statistically significant improvement was seen especially in CTV and PTV of axillary lymph nodes. Such advantage was not observed for supraclavicular nodes or internal mammary nodes. We did not find any meaningful difference in sparing the risk organs such as lung, heart, LAD, oesophagus, trachea, thyroid gland, or spinal cord within two groups. PO-1210 Postoperative breast radiotherapy using image registration of initial PET-CT before NAC K. Shiraishi 1 , S. Kumagai 2 , R. Uehara 2 , K. Kitazumi 3 , T. Chikamatsu 4

Conclusion