ESTRO 36 Abstract Book

S550 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective Immobilization and positioning are necessary in radiation therapy of head-and-neck patients. A 5-points mask offers stability, although large shifts of the shoulder (>1cm) routinely can occur. A wrong positioned shoulder can cause coverage loss or an increased critical structure dose. The purpose of this study was to decrease the shouldershifts by increasing the awareness of the RTT’s. Material and Methods In the period January 2014 till June 2016 head-and-neck patients were immobilized daily with a 5-points mask (2014/2015: CIVCO Medical solutions: Posicast®, 2016: Orfit Industries: Efficast® Push Pin)/Wedges 5 0 & 7 0 (Cablon Medical)/Head supports (2014/2015: CIVCO Medical solutions: Posifix® Supine Headrests, 2016 Orfit Industries: Raycast® Head supports regular density with lateral neck flaps). For each year, 10 patients with head-and-neck cancer were selected randomly. All patients had daily CBCT imaging (Varian Medical Systems). The position of both shoulders on the CBCT relative to the mask was quantified in inferior direction in Offline Review (Varian Medical Systems). Measurements were performed on the coronal plane, 1.5cm dorsal of the isocenter (Figure 1).

PO-0998 Comparison of the accuracy of different pillow for radiation therapy of head and neck cancer C.Y. Lin 1 , W.H. Yu 1 , C.Y. Lin 1 , J.T.C. Chang 1 1 Chang Gung Memorial Hospital, Department of Radiation Oncology, Taoyuan, Taiwan Purpose or Objective Random error occurring in daily treatment is always a serious concern in fractionated radiotherapy (RT). Image guided radiotherapy can partially solve some of these problems. However, the curvature of the cervical spine is still a problem. Change of spine curvature can easily result in a deviation of more than 3mm. Therefore, we initiate this study to evaluate the accuracy of different pillow used for radiotherapy and to eliminate the errors caused With the agreement of institutional review board, 71 head and neck patients were enrolled and randomly assigned to use different pillow for either primary or postoperative RT. The three different pillows including conventional pillow (CP, Silverman Headrests, CIVCO, medical solution), customized pillow with alpha cradle (AC, Smithers Medical Products, Inc. ), and Moldcare Head Cushion pillow (MP, Alcar Co, Inc.). All patients used head and shoulder mask for fixation. Daily on-board image (OBI) was acquired for evaluation and correction of set-up error. Change of curvature was measured by the movement of the vertebral body of first (C1) and 5 th (C5) cervical spine, comparing to the location on digital reconstructed image from CT simulation. Results Of all patients accrued, 34 patients received surgery and postoperative radiotherapy, and 13, 11, and 10 patients used CP, AC, and MP respectively. Thirty-seven patients received primary radiotherapy without surgery, and 14, 11, and 12 of them used CP, AC, and MP respectively. There were 1633 OBI acquired. In postoperative RT group, the absolute movement of C1 were 0.07±0.03 cm, 0.07±0.03 cm, and 0.09±0.03 cm, when CP, AC, and MP was used, respectively (p> 0.05). In RT group, the absolute movements of C1 were 0.07±0.03 cm, 0.06±0.02 cm, and 0.08±0.08 cm, when CP, AC, and MP were used, respectively (p> 0.05). In comparison the movement of C5, the absolute movements were 0.15±0.04, 0.21±0.07, and 0.16±0.72, when CP, AC, and MP was used in postoperative RT group, respectively (p> 0.05). In primary RT group, the absolute movements were 0.23±0.09, 0.14±0.05, and 0.15±0.03, when CP, AC, and MP was used, respectively. The movements of C5 in patients who used AC (p = 0.048) or MP (p = 0.05) were significant lower than patients who used CP in primary RT group. Conclusion Customized pillow could reduce setup error in patients who received primary radiotherapy but not postoperative radiotherapy. PO-0999 Control of rectal volume with Kampo formula during prostate radiotherapy: A prospective study J. Kobayashi 1 , T. Tahara 2 , Y. Matsuzaki 1 , Y. Ono 1 , J. Matsumoto 1 , H. Sato 1 , K. Onko 1 , Y. Kishimoto 1 , T. Tanino 2 , H. Sakaguchi 2 , N. Uchida 2 1 Tottori University Hospital, Radiology, Yonago, Japan 2 Tottori University Hospital, Radiation Oncology, Yonago, Japan Purpose or Objective During intensity-modulated radiation therapy (IMRT) for prostate cancer, volume and position of the prostatic gland, bladder and rectum should be kept stable to minimize adverse events such as radiation proctitis or rectal bleeding. For this purpose, keeping the rectal volume small is essential. Daikenchuto (DKT) is a traditional Japanese herbal (Kampo) formula used to treat patients with abdominal bloating or constipation and is by curvature change. Material and Methods

Results Three hundred CBCT scans (600 shoulder positions) were examined. Table 1 shows the shoulder shifts in inferior direction. In 2014 23% of the shoulders was positioned ≥15mm inferior relative to the mask. At the end of 2014 the results were presented at our institute. Extra awareness of the RTT’s resulted in a decrease of the shouldershifts ≥15mm (7%). After a second presentation in December 2015, the percentage of shifts ≥15mm decreased (3.5% vs. 7%) in 2016. The percentage of shifts 5mm ≤ x < 10mm increased relative to 2015 (34.5% vs. 24.5%). This might be due to lack of experience with the new type of masks.

Conclusion A presentation and discussion session is a simple and efficient way to create more awareness. Extra awareness of the RTT’s improved the setup of the shoulders in a 5- points mask, but the immobilization of the shoulders demands attention. The reason for the increase in shifts 5mm ≤ x < 10mm will be further investigated.