No abstract

Objective: Hippocampus-sparing whole-brain radiotherapy using Halcyon, an instrument dedicated to volumetric modulated arc therapy, has not been studied till date; hence, we aimed to examine whether it can meet the RTOG0933 criteria. Based on this, we compared Halcyon to Tomotherapy, which also uses an O-ring-type linear accelerator. Methods: This exploratory, experimental, and retrospective study used 5 sets of computed tomography images in the head area to investigate the planning target volume, hippocampal doses, and irradiation time. Calculations were performed from 1 to 4 arcs to determine the optimal number of arcs in the Halcyon plan, which were compared to those of Tomotherapy. Results: The Radiation Therapy Oncology Group 0933 criteria could not be satisfied in Halcyon with 1 arc. With 2 arcs, the condition Dmax<16 Gy was not satisfied for 1 case in the hippocampus. Since there were no significant differences between 3 and 4 arcs, including the irradiation time, 3 arcs were considered the best. We compared Halcyon at 3 arcs with tomotherapy and found that tomotherapy was inferior to Halcyon at D98%; however, it was superior to Halcyon in other dose parameters. In contrast, the irradiation time in Halcyon was overwhelmingly superior, with the irradiation time for Halcyon being 1/ninth the time for Tomotherapy. Conclusion: Halcyon was effective in handling hippocampus-sparing whole-brain radiotherapy. We believe that 3-arc radiation is best suited for this procedure. Although Halcyon was inferior to Tomotherapy in terms of dose distribution excluding D98%, it was overwhelmingly superior in terms of irradiation time.

Background: Patients with unresectable pancreatic cancer (PC) sometimes experience gastrointestinal bleeding (GIB) due to tumor invasion of the gastrointestinal tract (tumor bleeding), and no standard treatment has been established yet for this complication. Palliative radiotherapy (PRT) could be promising, however, there are few reports of PRT for tumor bleeding in patients with unresectable PC. Therefore, we evaluated the outcomes of PRT for tumor bleeding in unresectable PC patients. Methods: We reviewed the medical records of patients with unresectable PC diagnosed at our institution between May 2013 and January 2022, and identified patients with endoscopically confirmed tumor bleeding who had received PRT. PRT was administered at a total dose of 30 Grays (Gy) in 10 fractions, 20 Gy in 5 fractions, or 8 Gy in a single fraction, and the dose selection was left to the discretion of the radiation oncologists. Results: During the study period, 2562 patients were diagnosed as having unresectable PC at our hospital, of which 225 (8.8%) exhibited GIB. Among the 225 patients, 63 (2.5%) were diagnosed as having tumor bleeding and 20 (0.8%) received PRT. Hemostasis was achieved in 14 of the 20 patients (70%), and none developed grade 3 or more adverse events related to the PRT. The median time to hemostasis was 8.5 days (range, 7–14 days). The rebleeding rate was 21.4% (3/14). The median hemoglobin level increased significantly (p < 0.001) from 5.9 g/dL to 9.1 g/dL, and the median volume of red blood cell transfusion tended (p = 0.052) to decrease from 1120 mL (range, 280–3360 mL) to 280 mL (range, 0-5560 mL) following the PRT. The median overall survival (OS) was 52 days (95% confidence interval [CI], 39–317). Of the 14 patients in whom hemostasis was achieved, chemotherapy could be started/resumed in seven patients (50%), and the median OS in these patients was 260 days (95% CI, 76-not evaluable [NE]). Three patients experienced rebleeding (21.4%), on days 16, 22, and 25 after the start of PRT. Conclusion: This study showed that PRT is an effective and safe treatment modality for tumor bleeding in patients with unresectable PC.

No abstract