ESTRO 2023 - Abstract Book

S393

Sunday 14 May 2023

ESTRO 2023

= 0.52, standard deviation 1.03, range 0-4 for both groups). Only 1 patient in Group 2 required additional rectal preparation and was given suppositories up to fraction 20. The number of patients reporting CTCAE V4 Grades 1-2 for colitis, diarrhoea, nausea, proctitis and rectal pain was equal between the 2 groups. The number of patients reporting CTCAE V4 Grades 1-2 for anal / rectal bleeding in group 1 was significantly higher than group 2 (Group 1: n=5, Group 2: n=1). The patient in Group 2 who required daily suppositories to achieve an empty rectum was the only patient in that cohort who reported CTCAE V4 grade 2 anal/rectal bleeding. Conclusion The number of repeated CBCT scans at fractions 11-20 for bowel issues were similar between groups. This demonstrates that enemas are not necessary to improve plan reproducibility for fractions 11-20 for the majority of patients undergoing radiotherapy to the prostate. Reducing enema use from 20 to 10 fractions resulted in fewer patients experiencing anal / rectal bleeding at week 4 of radiotherapy. In conclusion, enemas for fractions 11-20 should not be given routinely to all patients as they do not improve plan reproducibility and may increase anal / rectal bleeding. PD-0485 Open-face vs. closed masks: a randomized trial assessing patient comfort in cranial radiotherapy M. Keane 1 , K. Tomuschat 1 , R. Dal Bello 1 , S. Perryck 1 , S. Tanadini-Lang 1 , I. Madani 1 , M. Guckenberger 1 , M. Brown 2 1 University Hospital Zürich, Department of Radiation Oncology, Zürich, Switzerland; 2 University Hospital Zürich, Department of Radiation Oncology, Zürich, Switzerland Purpose or Objective Standard immobilization for fractionated cranial radiotherapy is a closed thermoplastic mask, which allows for stable and reproducible patient positioning. This randomized trial investigated patient comfort and preference of open-faced masks compared to closed masks in patients undergoing partial or whole brain irradiation. Materials and Methods In this single-centre prospective randomized self-controlled trial, patients were treated sequentially with two immobilization masks and identical treatment plans, each used for 50% of the prescribed treatment. The order in which the masks were used was decided using crossover randomization. The primary endpoint was patient comfort. Participants completed a Visual Analogue Scale (VAS) assessment after the first fraction and weekly thereafter, scoring separately their levels of each discomfort, anxiety and pain on a 10-point scale. Where present, patients indicated the anatomical location of pain on a diagram. On the last fraction, patients reported their mask of preference. The secondary endpoint assessed inter- and intra-fraction stability between the masks. Inter-fraction set-up uncertainties were assessed using daily orthogonal kV imaging. An SGRT system was used with the open-face masks to report intra fraction motion and aid patient positioning. Intra-fraction mask stability was assessed using kV imaging once weekly post treatment. Results A total 30 patients with primary or secondary brain tumors were registered to the trial, with 29 completing treatment to a median radiation dose 54Gy, range 30-60Gy. Discomfort VAS scores were significantly lower for open-face masks (mean VAS score 0.5, standard deviation [SD] 1.0) compared to closed (mean VAS score 3.3, SD 2.9), P<0.0001 (Fig.1.). Mean VAS score for anxiety (0.2 [SD, 0.6] vs. 1.2 [SD 1.8] for closed masks) and pain (0.2 [SD 0.6] vs. 1.7 [SD 2.5] for closed masks) were also significantly lower for open-face masks, P<0.0001. Closed masks were associated with significantly increased discomfort in infraorbital (P<0.001) and maxillary (P=0.02) areas. 18 of 20 (90%) participants indicated that they preferred the open-face mask over the closed mask. The remaining participants gave no indication of a preference. Mean inter fractional longitudinal, roll and yaw shifts were significantly larger for open-face masks: 2.3±5.8 mm, 0.8±0.60 and 0.8±0.70, respectively versus 1.7±1.7 mm, 0.7±0.60 and 0.8±0.60 for closed masks (Table 1.). No significant difference in intra-fraction variability was observed.