ESTRO 38 Abstract book

S764 ESTRO 38

Nakayama 1 , J. Itami 1 , N. Murakami 1 , S. Nakamura 1 1 National Cancer Center Hospital, Radiation oncology, Tokyo, Japan Purpose or Objective It is well known that significant variations in stomach size, shape, and respiratory motion lead to uncertainties in target localization during treatment for stomach. For this reason, planning target volume (PTV) margin is large for the external beam radiation therapy (RT) of gastric mucosa-associated lymphoid tissue -guided-online-adaptive- radiotherapy is a promising tool for gastric radiotherapy. Our online-adaptive-radiotherapy (On-line ART) process relies on daily image overview by the managing radiation- oncologist, who determines the need for creating a predicted plan if significant inter-fractional anatomical changes are noted. In this study, the usefulness of MR guided adoptive radiation therapy of gastric MALT lymphoma was evaluated. Material and Methods Fifty-nine years old female patient with gastric MALT lymphoma underwent breath-hold radiotherapy on the MRI-cobalt system (ViewRay MRIdian system, Oakwood Village, OH, US). The prescribed dose to PTV (defined as a 5 mm expansion of the entire stomach) was 24 Gy in 12 fractions. The patient was instructed to not eat or drink starting four hours prior to treatment. Sagittal slice cine- MR images were acquired through the center of the stomach at 4 frames per second throughout the treatments. Clinical target volume (defined as the entire stomach) and organ at risks (OARs) were contoured on the first frame of the MR cine and tracked for the first 20 min of each treatment using offline optical-flow based deformable registration. Results The patient underwent RT as scheduled, without any significant adverse effects. MR-guided gating was performed with beam off when ≥10% of the stomach volume exceeded the 3.0-mm boundary expansion.Significant inter-fractional stomach variations on the order of 5.0 cm were observed.N = 12/12 fractions were adapted based on On-line ART. The mean dose of the CTV was 23.79 Gy (V100 = 99.13%). Conclusion Superior soft-tissue visualization combined with the MR- guided RT ability to dynamically adjust the treatment plan and/or gate the treatment delivery to account for intra- fractional anatomical changes offers great promise to further enhance treatment precision for gastric sites. This approach brings valuable opportunities to decrease overall toxicity profiles. EP-1404 SBRT as definitive treatment of adrenal gland metastases: a single center experience O. Hernando Requejo 1 , M. Peñacoba 2 , E. Sanchez Saugar 1 , M. Lopez Gonzalez 1 , X. Chen 1 , R. Alonso Gutierrez 1 , A. Montero Luis 1 , R. Ciervide Jurio 1 , J. Valero Albarran 1 , M. Garcia-Aranda Pez 1 , P. Fernandez Leton 3 , J.M. Perez Moreno 3 , J. Garcia Ruiz-Zorrilla 3 , D. Zucca Aparicio 3 , L. Alonso Iracheta 3 , M.A. De la Casa de Julian 3 , J. Marti Asenjo 3 , B. Alvarez Rodriguez 1 , A. Acosta Rojas 1 , J. Plama Delgado 1 , M.C. Rubio Rodriguez 1 1 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Oncology, Madrid, Spain ; 2 Hospital Universitario Marques de Valdecilla, Radiation Oncology, Madrid, Spain ; 3 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Physics, Madrid, Spain Purpose or Objective Adrenal gland metastases are a common problem in oncology, causing abdominal pain, nausea and vomiting, (MALT) lymphoma. Magnetic-resonance (MR)

leading to patient discomfort. Classical treatment includes surgical resection or chemotherapy, being palliative conformal 3D Radiotherapy the only non- invasive local treatment available. Recently new definitive treatment modalities such as Radiofrequency ablation and SBRT have been developed with promising results. The aim of this study is to analyze the safety and efficacy of SBRT treatment for adrenal gland metastases. Material and Methods From April 2008 to September 2018 a total of 32 selected patients have been treated of adrenal gland metastases with SBRT at our Institution. Treatment techniques included fiducial-based Adaptive Respiratory Gating (7 patients), Dampening (19) and Active Breathing Coordinator (6). Treatment planning included 7 patients with VMAT, 11 with 3D Conformal Radiotherapy and 6 with IMRT (Fig1). Toxicity was evaluated with CTCAE v5.0. Statistical analysis included descriptive tests and Kaplan Meier curves for survival.

Results All patients (18 males and 14 females) completed treatment as scheduled. The most common location of the primary tumor was lung (75%). Other locations were: gynecological (6%), colorectal, melanoma and sarcoma (3% each). Sixteen patients received SBRT for right adrenal gland, 15 for left gland and 1 for both glands. Median dose of 47 Gy (range 24-60 Gy) and median dose/fraction of 12 Gy (range 5-20 Gy) was administered. The median PTV size and volume was 31 mm and 57 cc respectively. With a median follow up of 13.2 months local control crude rate was 88.89%. Five patients achieved a complete response, 11 partial response, 7 stable disease and 3 local progression. Estimated local control at 16 months was 77.3%. Median local failure free survival was not reached. Other distant metastases appeared in 85.2% of patients. Median overall survival was 12 months. Fifty seven percent of patients were alive at 12 months. As prognostic factors we found that left adrenal metastases had statistically significant worse local control than right adrenal ones, which is straightly related with the total dose administered. Doses with BED above 100 Gy (BED-α/β 10 ) had statistically significant better local control than those treated with BED of 100 Gy or below (Fig2). Local control after SBRT was not related with overall survival.