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often delivering significantly less than the prescribed dose to the target volume, there is a suggestion that a lower dose more accurately delivered may be sufficient to achieve similar outcomes.

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Evaluating the accuracy of ultrasound Iocalisation for positioning prostate cancer patients for external beam radiotherapy J. Coffev I, H.A. McNair 2, B. Shoulders 2, V.N. Hansen 3, S.A. ~4anga/, J. Staffurth ~, A.S.N. Jackson 1, S.A. Sohaib 4, D.P. Deamale/ ~ Royal Marsden Hospital, Academic Urology Unit, Sutton, United Kingdom 2Royal Marsden Hospital, Radiotherapy Department, Sutton, United Kingdom 3Royal Marsden Hospital, Physics Department, Sutton, United Kingdom 4Royal Marsden Hospital, Radiology Department, Sutton, United Kingdom Purpose: To evaluate the accuracy of the ultrasound based (BAT®SXi, Nomos Corp.) system for Iocalisation of prostate position compared to CT Iocalisation.

Materials and Methods: Prostate alignments using the BAT system were evaluated in the first nineteen of a projected twenty five patients. The BAT system was calibrated daily to the CT isocentre, thus if the BAT located the prostate in the same position as in the CT scan, the couch adjustment would be zero. Patients underwent an initial CT scan in the treatment position and the prostate, bladder and rectum were outlined. BAT ultrasound was then performed, capturing transverse and sagittat suprapubic ultrasound images, approximately 30 minutes later, whilst the patient remained in the same positin on the planning couch. The corresponding CT contours were imported into the BAT system and overlaid onto the ultrasound images and the necessary couch shifts were recorded to produce the alignment (US). In order to evaluate inter-user variability these measurements were taken by three different operators. To account for patient and prostate movement between the CT and the ultrasound, a second CT planning scan was taken approximately 30 seconds after the BAT ultrasound, again with the patient in the same position, and fused with the initial CT to determine any patient or prostate movement(CT2-CT I=CTM (. These measurements were deducted from the original BAT measurement to determine the accuracy of the BAT compared to CT (US-CTM (. Results: The BAT ultrasound system produced good quality images that were reproducible between different operators. Inter-observer variability was minimal. Table below shows the mean and SD displacements, in centimetres, in each direction.

CT,-uslnitial couch shifts: ! 0 .3 (0.9){0.4; (0.4) 0.2 (0.3)

Organ and patient movement ^ ,_ _, 0 (0.3) u (u.4) 0 (0.b)

CTz.CTI=CTM

Accuracy of BAT system: 0.3 (0.6) 0.3 (0.4) 0.2 (0.3)

U S -CTM

Conclusions The BAT ultrasound system proved to be mobile, non invasive and quick to use. The ultrasound images gained were reproducible by all users and showed little inter-observer variability. The mean displacement of the

BAT compared to the CT scan was <0.3cm in all directions. However, there was a larger SD in the S/I than in the A/P

and PJL direction. This may have arisen from the difficulty in determining the inferior aspect of the prostate on the sagittal ultrasound views.

1084 poster

3D postoperative chemoradiation in gastric carcinoma: acute toxicity and treatment feasibility F. Cellini 1, E. D'Angelo 1, G. C. Mattiuccf , A. Caiazza ~, G. ~ , L. Di Lullo 3, F. Deodato 2, P. Murino 2, D. D'Ugo 4, V. Valentini ~ I Universit~ Cattolica S. Cuore, Radioterapia, Roma, Italy 2Universit& Cattolica S. Cuore, Radioterapia, Campobasso, Italy 30spedale Civile, U.O. Oncologia, Isernia, Italy 4Universita Cattolica S. Cuore, U.O. Chirurgia, Campobasso, Italy Introduction: The results of U.S.Intergroup 0116 demonstrated that concomitant chemoradiation improves local control and overall survival in resected gastric carcinoma. However postoperative chemoradiation was associated with major probability of severe toxicity. Therefore only 64% of the patients completed the prescribed combined modality treatment.

Material and methods: 27 patients (median age:60 ys; M/F:16/11) were treated with postoperative chemoradiation after surgical resection. Pathological stage (UICC 2002) was as follow: la: l ; Ib: l ; 11:4; Illa:12; IIIb:3; IV:6. Tumor site was: Upper Third:7 (25.9 %); Middle Third:8 (29.6 %); Lower Third: 12 (44.5%). 19 (70.4%) patients received 45 Gy (1.8Gy/fract.) over five weeks plus adjuvant and concurrent 5-Fu according to Intergroup 0116 study. 8 (29.6%) patients with major risk factors received a 9 Gy boost to the tumor bed; in these patients 5-Fu was delivered by continuous i.v. infusion (225 mg/day) during the entire treatment. Radiotherapy was delivered by CT based 3D-conformal technique. The dose was prescribed according to ICRU 62.

Results: 25/27 (92.5%) patients completed the entire combined modality treatment. One patient definitively interrupted the radiation therapy after 27 Gy delivered due to a GI Grade 3 toxicity, and severe PS worsening. Another patient definitively interrupted the concurrent chemotherapy due to GI Grade 4 toxicity. Two (7.4%) patients had a temporarily treatment interruption due to toxicity. Overall 2/27 (7.4%) patients had a GI Grade 3 toxicity, 1/27 (3.7%) had a GI Grade 4 toxicity, 1/27 (3.7%) patient had a grade 3 thrombocytopenia.

Conclusions: In spite of the relatively low number of patients, this analysis seems to suggest that 3D conformal therapy improves tolerance and feasibility of postoperative concurrent chemoradiation in gastric cancer.

1085 poster

Correlation between the movement of the chest wall and the movement of the target volume in 3D-radiotherapy of the oesophagus cancer using the gating technique J. Dumas 1, F. Lorchef, C. Gaffard 2, C. Poirot 2, A. No~i 3-4, J. Bosset ~, P. Alettf -4, D. Wolf 4 ~University Hospital, Radiotherapy, Besan~on, France 2Postgraduate Institute of Ingineers of Franche-Comte , Besan~on, France 3Centre Alexis Vautrin , Radiotherapy, Nancy, France 4Polytechnic National Institute of Lorraine, CRAN CNRS UMR 7039, Nancy, France