ESTRO 2020 Abstract Book

S655 ESTRO 2020

Purpose or Objective Neuropathic pain (NP) is a source of distress in patients with bone metastasis (BM) and notoriously resistant to pharmacological intervention. Tapentadol is an opioid with a dual mechanism, expected to be better to treat NP than other opioids, but has no established clinical evidence for cancer related NP. Only one randomized trial explored the role of RT for NP, comparing an 8 Gy single fraction with 20 Gy/5 fractions. There is no study assessing the utility of specific medication targeting neuropathic pain together with palliative RT. The aim of our pilot study was to assess pain response rate (RR) and quality of life (QLF) in patients presenting moderate/severe NP with a novel treatment approach based on tapentadol and 3D-RT. Material and Methods We conducted a prospective multicenter (3 centers) pilot study of patients undergoing palliative RT for painful BM between 2014 and 2017. Patients were assessed before RT using the validated screening DN4 questionnaire (Douleur Neuropathique en 4 questions) to identify NP components. Pain numeric score (0-10) and analgesic intake were recorded and response to RT (8Gy-30Gy/1-10fr) was assessed according to the criteria defined by the International Bone Metastases Consensus. Inclusion criteria: radiological evidence of BM from a known malignancy, NP according to DN4 (cut-off score ≥4), no clinical/radiological evidence of spinal cord compression, worst pain (last 72 hours) numeric score ≥5/10. Endpoints: pain response and QLF assessment with EORTC QLQ-c30 and BM-22 module 1 month and 2 months after the end of RT. The Kruskal-Wallis nonparametric and Wilcoxon rank sum tests compared changes in QOL among response groups Results

Sixteen patients with CNS tumors received PT between 2015 and 2019. During follow-up, MRI was performed to monitor the appearance of neuroradiological toxicities: the first 1 month after PT, then every 3 months for the first year and later every 6 months in case of symptom absence. Acute and late toxicities were recorded according to the CTCAE, v4. Median age at PT was 6 years [13 months – 17 years], M/F: 10/6. All patients underwent surgery (3 total, 10 subtotal/partial, 3 biopsies) before PT. Eleven received chemotherapy (5 with autologous stem- cell rescue) before PT and 5 after PT. Median total dose to the primary tumor site was 54 CGE in 1.8 CGE daily fractions; furthermore, 10 patients received craniospinal irradiation (CSI): seven at 36 CGE, 3 at 23.4 CGE. Twelve patients received PT with daily anesthesia. Tumor histologies were as follows: 8 Medulloblastomas (MB, 3 SR and 5 HR); 2 Pilocytic Astrocytomas (PA), 3 Atypical Teratoid/Rhabdoid Tumors (AT/RT), 1 pure Germinoma, 1 Choroid Plexus Carcinoma (CPC) and 1 clear-cell invasive Meningioma. Results At a median follow-up time of 25 months [9 – 47 months], 15 patients are alive: 8 complete response, 6 stable disease, 1 progressive disease; one patient died due to disease progression. Two out of 16 patients developed early neuroradiological toxicities: a 10-year-old patient with HR-MB (who had received 36 CGE CSI plus a 19.8 boost) at 3 months after PT developed a G3 PRES during chemotherapy, which resolved completely. A 1-year-old meningioma patient at 3 months after PT developed a symptomatic perilesional edema (G3) in the irradiated area to 54 CGE, with full recovery after medical therapy. Both patients also developed small asymptomatic cavernomas inside or close to the irradiated volume, respectively at 3 and 5 months after PT. Five patients showed late neuroradiological toxicities: 1 patient with CPC, 1 with HR-MB and 1 with AT/RT developed small asymptomatic cavernomas at 21, 9 and 6 months after PT, respectively; all three were ≤3 years old at the time of PT. The former two had received 36 CGE CSI plus a 19.8 boost, while the latter 54 CGE on the primitive. A 2-year-old AT/RT patient developed after 15 months an asymptomatic Moyamoya arteriopathy. A 17-year-old patient with HR-MB developed a self-limiting intracranial bleeding (G2) 24 months after PT, in a site that had received 54 CGE. Conclusion We observed limited neuro-radiological toxicities and no radio-necrosis. The result is notable considering the young patient age (6 patients < 4 years old). The incidence of cavernomas seems to be more frequent in patients treated with whole brain irradiation although the number of cases is still limited. A longer follow-up and more patients are needed to better evaluate toxicities after PT. PO-1245 Novel approach in bone metastasis with neuropathic pain: palliative radiotherapy with tapentadol? J. Cacicedo 1 , J.P. Ciria 2 , V. Morillo 3 , L. Martinez_Indart 4 , A. Gomez-Iturriaga 5 , O. Del Hoyo 5 , A. Frias 5 , D. Büchser 5 , I. San Miguel 5 , F. Suarez 6 , A. Gonzalez 6 , F. Casquero 5 1 Cruces University Hospital/Biocruces Health Research Institute, Radiation Oncology, Barakaldo, Spain ; 2 Hospital Universitario Donostia, Radiation Oncology, San Sebastian, Spain ; 3 Hospital Provincial Castellon, Radiation Oncology, Castellon, Spain ; 4 Biocruces Health Research Institute, Biostatistics, Barakaldo, Spain ; 5 Hospital Universitario de Cruces/Biocruces Health Research Institute, Radiation Oncology, Barakaldo, Spain ; 6 Hospital Universitario de Cruces, Radiation Oncology, Barakaldo, Spain Poster: Clinical track: Palliation