ESTRO 36 Abstract Book

S551 ESTRO 36 _______________________________________________________________________________________________

reported to increase intestinal motility. DKT is composed of three medical herbs (ginger, ginseng radix, Japanese pepper) and maltose powder. The purpose of this study was to investigate the effect of DKT on rectal volume during prostate IMRT prospectively. Material and Methods The institutional review board approved this study and written informed consent was obtained from all patients. We divided consecutive 30 non-metastatic (cT1cN0 to cT3bN0) prostate cancer patients into two groups. 15 patients were orally administered 15 grams of DKT per day from one month before IMRT until the last day of the treatment (DKT group). The remaining 15 were not administered DKT (non-DKT group). The prescribed radiation dose was 78 Gy in 39 fractions for 7.5 weeks to the prostatic gland and proximal one-third or entire seminal vesicle according to their stratified recurrence risk. Kilo-voltage computed tomographic image (KV-CT) by linear accelerator (Trilogy, Varian Co.) was taken for three-dimensional matching set-up before each treatment session. Each KV-CT was sent to a radiation treatment planning workstation (Pinnacle 3, Phillips Medical Systems Co.) and rectal volume of anal-sided 8cm length was then measured. Calculated rectal volumes of the DKT group were compared to those of the non-DKT group. Administration of laxative agent, tubal gas suction or colon irrigation was done depending on residual rectal content before radiation. Results Total of 1,170 KV-CT were evaluated. Rectal volumes of DKT and non-DKT groups were 48.79-63.46 (mean 54.69 +/- 4.00) cm 3 and 52.41-142.57 (mean 81.37 +/- 16.36) cm 3 , respectively (p < 0.01). Adverse effects associated with DKT use such as appetite loss, liver dysfunction or interstitial pneumonia were not noted.

support, and to evaluate which of these systems was best suited for stereotactic brain treatments. Material and Methods Patients receiving brain RT were treated with either one of three different fixation systems (Orfit Industries, see figure 1): a hybrid mask combined with (a) an individual head support vacuum bag (n=20); (b) a Thermofit individual head support(n=17); (c) a standard 3D head support with cranial stop (n=10). All patients received a correction protocol and were imaged at least 3 times during the treatment course using an Elekta XVI CBCT, both before and at the end of the treatment fraction. All scans were registered on bony anatomy and translations and rotations were recorded and analysed. For the three different fixation systems the mean (M), systematic (Σ) and random (σ) errors were determined over the patient population for the intrafraction translations and rotations, and interfraction rotations.

Results Figure 2 shows the systematic and random errors of the intrafraction translations (a,b) and interfraction rotations (c,d) of the three different fixation systems. Intrafraction translations were small for all systems, with maximum deviations generally lower than 1 mm for all fractions, and a systematic and random error both in the order of 0.3 mm. No statistically significant differences were found between the vacuum bag and Thermofit system, while the 3D head support showed a slight improvement for the systematic errors compared to the individually moulded head supports. Intrafraction rotations were typically in the order of 0.2 ⁰ , and no differences were observed between the three groups. The systematic and random errors of the interfraction rotations were in the order of 1 ⁰ and 0.6 ⁰ for all systems, with no significant differences between the three fixation systems, and maximum rotations of up to 4 ⁰ were observed occasionally.

Conclusion DKT appears to be useful in reducing rectal volume and intra-fractional volume variance which would help prevent radiation proctitis or rectal bleeding in prostate curative radiotherapy. Longer follow-up with a larger patient population is desired. PO-1000 Immobilisation systems for brain treatment: are individual head supports needed for stable fixation? S. Meessen 1 , F. De Beer 1 , P. Van Haaren 1 , D. Schuring 1 1 Catharina Hospital Eindhoven, Department of Radiation Oncology, Eindhoven, The Netherlands Purpose or Objective For stereotactic treatment of brain metastases, good fixation of the patient is necessary to enable the use of small PTV margins and reduce the volume of healthy brain tissue receiving high doses. These fixations should prevent significant intrafaction movement, and reduce the interfraction rotations. The purpose of this study was to compare three different fixation systems, two with individual head supports and one with standard head