ESTRO 2021 Abstract Book

S440

ESTRO 2021

terms of tumor response, downstaging, and survival. Though the number of involved cases was small, resection margin status and ypN stage are considered the main prognostic factors irrespective of initial disease status and applied thermal energy.

PH-0554 Re-irradiation and concurrent Hyperthermia for recurrent brain tumors: an initial experience C. Silva 1 , M. Amorim 1 , M.A. Costa 2,1 , C. Fardilha 2,1 , J. Conde 2,1 , G. Campos 2 , P. Genésio 2 , A. Moreira Pinto 3 , A. Cruz 3 , P. Costa 2,1 1 Hospital de Braga, Radiation Oncology, Braga, Portugal; 2 CUF Institute, Radiation Oncology - Júlio Teixeira S.A., Porto, Portugal; 3 CUF Hospital, Medical Oncology, Porto, Portugal Purpose or Objective Although many approaches for recurrent brain tumors (RBT) have been evaluated, there is no standard treatment in such cases. Radiation oncologists have been cautious about re-irradiating brain tumors because the risks of high incidence of acute and late toxicity in the central nervous system (CNS), namely edema and necrosis. Hyperthermia (HT) increases the sensitivity of tumor cells to ionizing radiation and its association to Radiotherapy (RT) has been demonstrated in a wide variety of oncological settings. The purpose of the present study is to evaluate the tolerability and efficacy of re-irradiation (re-RT) with HT for patients with RBT. Materials and Methods Between August 2016 and February 2020, 8 patients with the diagnosis of recurrent brain tumors were treated with re-RT and HT in our institution. The initial therapeutic approach was surgery, RT (60Gy in 30 fractions) with concurrent Temozolomide-based chemotherapy, followed by maintenance chemotherapy. Treatment for recurrent disease was re-RT with concurrent HT, performed after palliative debulking surgery and chemotherapy (Irinotecan plus Bevacizumab). Results There were 6 male and 2 female patients. The median age at diagnosis was 52 years, range 38-65. The predominant histology was glioblastoma multiforme (6 cases), followed by hemangiopericytoma (2 cases). The median interval between initial RT and re-RT was 30 months (range 15-60). The average tumor volume was 39,76cc for CTV (range 22,18-54,14) and 73,71cc for PTV (range 51,50-83,69). RT was delivered at a dose of 30Gy, in 5-10 fractions. The HT treatment was performed twice a week, for 20-45 minutes, up to 1 hour after RT, with a Celsius 42+ device, using two 150-mm electrodes, to deliver radiofrequency at 13,56MHz. The treatment goal was to achieve 40-43ºC. All patients completed the prescribed treatment, except for 1 patient, due to a pneumothorax. Headache and nausea were observed in 1 case, treated with corticosteroid therapy. The remaining patients presented good tolerance to re-RT and concurrent HT, with no acute toxicity. The median OS was 15,5 months (range 2-36). Conclusion Tumor progression occurs frequently in malignant brain neoplasms, despite local aggressive therapies performed. Therapeutic effect of Hyperthermia in association with Radiotherapy has been extensively demonstrated in a wide variety of oncological settings, playing an important role in recurrent disease treatment. This approach represents an additional option for patients in whom there are few valid therapeutic proposals to present, as in recurrent brain tumors. Radiotherapy association to Hyperthermia results in an additive tumoricidal effect, with acceptable toxicity. Further studies are needed to evaluate the role of this treatment association in such cases. PH-0555 Modulated electro-hyperthermia plus systemic cancer treatment in digestive cancer. A safety study. E.E. Arrojo Alvarez 1 , J.C. Mazabuel Quintero 2 , D. Arribas Crespo 2 , A. Serrano Escalada 2 , J. Anchuelo Latorre 3 1 Medical Institute of Advanced Oncology (INMOA) ; University Hospital Marqués de Valdecilla, Radiation oncology, Madrid; Santander, Spain; 2 Medical Institute of Advanced Oncology (INMOA), Radiation Oncology, Madrid, Spain; 3 University Hospital Marqués de Valdecilla, Radiation Oncology, Santander, Spain Purpose or Objective Tumor vasculature is usually poor, narrow and aberrant, which can significantly limit oncological systemic treatment (OST) distribution and therefore effectiveness. This is usually more significant in more aggressive malignant tumors. Modulated electro-hyperthermia (mEHT), also known as oncothermia, has been proved as a selective type of hyperthermia for malignant tumors, which vasodilates only intratumoral vessels improving chemotherapy distribution inside the tumor, and minimizing the risk of other hyperthermias that create a general vasodilation in the treatment area, which could potentially increase the risk of distant metastases. Due to its selectivity, the risk of side effects from mEHT treatment is also very low. Up to date, there is only one phase III study with mEHT+chemotherapy and radiotherapy in cervical cancer patients with wonderful results. The purpose of this study, is to evaluate the safety of an mEHT treatment concomitant to OST (chemotherapy, immunotherapy, antiangiogenic therapy…) for digestive cancer. Materials and Methods We retrospectively analyzed data from patients treated at the Medical Institute of Advanced Oncology (INMOA) between July 2019 and January 2021 for digestive carcinoma stage IV treated with OST plus mEHT applied at the abdominal area. CTCAE v5.0 grade scale was used for evaluating toxicity. Results 51 patients with stage IV cancer treated for digestive cancer with intraabdominal metastases were evaluated. Median age was 59 years (35-85). There were 25 females and 26 males. Most of the patients had colon (31%) or pancreatic cancer (31%), while 22% of the patients had gastric cancer, 6% cholangiocarcinoma, 4% esophagus, 4% rectal and 2% GIST. Metastatic site was liver in 80,4% of the patients and peritoneum in 20% of the patients. All patients were treated for at least 12 mEHT treatments and received at least 2 OST cycles concomitant to mEHT treatment. All mEHT treatments, were applied non consecutive days and had 90 minutes length. mEHT power range was between 80 and 150W.