ESTRO 2025 - Abstract Book

S1583

Clinical – Mixed sites & palliation

ESTRO 2025

4225

Digital Poster Half-body irradiation with the possibility of escalated dose under the spotlight of newer systemic therapies: the dawn of new therapeutic chances? Valentina Zagardo, Gianluca Ferini Radiotherapy, Radioterapia REM srl, viagrande, Italy Purpose/Objective: To evaluate the safety and efficacy of half-body irradiation (HBI) in improving quality of life, reducing analgesic intake, alleviating pain intensity, and, secondarily, achieving local disease control. Additionally, we hypothesized that a higher biological equivalent dose (BED) would lead to an increased objective response rate (ORR) and enhanced pain relief. Material/Methods: We retrospectively queried our mono-institutional database to identify patients with painful widespread bone metastases from solid tumors who underwent HBI. The primary study outcomes included the pre- and post radiotherapy(RT) pain levels, pre- and post-RT analgesic consumption, and treatment-related toxicity. Secondary outcomes included the ORR, local control (LC), progression-free survival (PFS), and overall survival (OS). Results: Twenty-three patients met the inclusion criteria. As one patient underwent irradiation twice, the total number of HBI was 24. In 9 out of 24 treatments, a higher dose than those commonly used was administered; of these, 6 patients were treated with a simultaneous integrated boost (SIB). Overall, nearly all patients reported immediate pain relief, with 35.71% achieving complete pain resolution. Among these, 62.5% were treated with a higher dose. Additionally, better outcomes were observed in patients with breast cancer histology, where nearly half achieved complete pain relief. Before RT, 82.60% of patients were using analgesics, ranging from acetaminophen to opioids. After RT, 21.05% continued their pre-RT regimen, 21.05% reduced their dosage or switched to less potent analgesics, and 52.63% discontinued pain medications. Regarding ORR, 5 complete responses were recorded out of 14 available imaging assessments, 4 of which involved treatment with a higher dose. Two patients experienced local relapse or progression, none of whom received SIB. Overall, five patients died. In terms of toxicity, three out of twenty-three patients required blood transfusions within one month following RT due to severe anemia, while two patients experienced a significant decrease in platelet counts. No additional toxicity was observed in patients treated with SIB.