Development of a TLD calibration system for 192Ir HDR and PDR sources for the ESTRO ESQUIRE BRAPHYQS project

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Long-term results in choroidal and ciliary body melanoma after ruthenium brachytherapy (a 15 years experience). F. Rouberol2, O. Chapet 1, J.M. Ardiet 1, P. Romestaing 1, J.D. Grange 2, J.P. Gerard3 1CH Lyon Sud, Radiation Oncology, Pierre Bonito CEDEX, France 2Hop Croix-Rousse, Eye cfinic, Lyon, France 3C. A. Lacassagne, Nice, France Purpose: analyze overall survival, local recurrences, radiation-induced complications, enucleations and visual loss after brachytherapy of malignant uveal melanoma with ruthenium-106 plaques (106 Ru BT). Patients and method: between 06/1983 and 01/1995, 213 patients with uveal melanomas (92 m and 121 f, age 22-84) were treated with 106Ru BT in Lyon. 28% of tumors were posterior, 67% anterior, 5% mixed. Median tumor diameter was 9mm, and median height 5mm. Tumors staging was: T1=19%, T2=36%, T3=45%. Treatment: brachytherapy with ruthenium-106 plaques (106Ru BT), either alone (183 pts), or with a second 106Ru application (15 pts), or 192Iridium (5 pts), or complementary proton (10 pts). Dose and plaque size were determined according diameter, thickness and location of T. Dose to tumor apex was 60Gy (safety margin=l mm). A second treatment was done for tumors with initial thickness > 7 mm. Results: 5 and 1.0year overall survival rates are 82% and 72% respectively. 5 and 10year probabilities of having no local recurrence are 66% and 60%, and the probabilities of not undergoing enucleation are 70% and 63%. There are two types of local recurrence: progression after initial remission (type 1); progression despite extensive treatment (type 2); 16% pts had type 1 and 6.5% type 2 local rec. A visual acuity < 20/100 was observed in 27% cases of anterior tumor but in 81% cases of posterior tumor (p < 0.001). 18% of pts underwent enucleation (local rec.: 13; blindness with neovascular glaucoma : 12; extrascleral tumor growth: 2). Comolications: Maculopathy was observed in 29% pts, retinal vascular occlusion in 17%, cataract in 12%, vitreous hemorrhage in 14%, neovascular glaucoma in 7% and optic neuropathy in 8.5%. Significant lower risks of maculopathy were observed for pts > 60 years (RR: 0.45) and anterior tumors (RR: 0.035). Risk for vascular occlusion decreased with age and anterior location (RR: 0.37). Conclusion: 106 Ru BT is effective in treatment of small T1 or T2 choroidal melanomas with anterior location. Overall survival is similar to that of others series with physical/surgical treatment and enucleation is avoided in 82% of pts. Many recurrences occur due to high proportion of T3. Complications are infrequent in patients with anterior tumors, and functional visual acuity is often retained. 65

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Dose evaluation in intraoperative HDR brachytherapy (IOBT) for rectal cancer: standard plans versus individual planning I.K. Kolkman-Deurloo 1, J.J. Nuyttens 2, PE. Hanssens2, P.C. Levendag 2 1Erasmus MC - Daniel Den Hoed Cancer Center, Radiation Oncology Clinical Physics, Rotterdam, The Netherlands 2Erasmus MC - Daniel Den Hoed Cancer Center, Radiation Oncology , Rotterdam, The Netherlands Introduction: In the Erasmus MC-DDHCC, IOBT is used as part of a multimodality treatment for locally advanced primary or recurrent rectal tumors since 1997. The IOBT is administered through a 5 mm thick Flexibel Intraoperative Template (FIT) positioned on the target area, with the size and shape of the FIT adjusted to the target for each patient. The target area is delineated by clips placed during the surgery. To reduce the total procedure time, treatment planning during IOBT is performed using flat standard geometries (standard plan), that neglect the curvature of the FIT. To evalu-

ate our procedure, we recalculated the treatment plan based on the real geometry of the FIT (individual plan) and we calculated the dose at the clips. Materials and methods: Thirty two patients were evaluated. The mean number of catheters was 8 (5-14), with a mean of 146 dwell positions (49-341). The prescribed dose was 10 Gy at 10 mm from the FIT surface. The standard plan was compared with the individual plan in terms of the average dose in all dose points and in a selection of fiv e dose points. One dose point was chosen centrally in the target area and four on each corner. The number of clips placed in each patient varied between 0 - 7 (mean 3.5). The dose was calculated in 134 clips. However, to know the gap between the FtT and the target surface, the 113 clips perpendicular under the FIT could only be used. Results: A mean treatment dose of 9.55 4- 0.21 Gy was found for the individual plan, compared to the prescribed 10 Gy (p<0.0001). The mean central dose was 10.03 4- 0.10 Gy in the standard plan and 9.20 4- 0.32 Gy in the individual plan (p<0.0001). The mean dose at the corners of the FIT was 10.3 Gy in the standard plan and ranged between 10.3 and 10.5 Gy in the individual plan. tn 71 of the 113 clips, the dose was larger than 15.0 Gy, corresponding to a gap smaller than 5 mm. tn 20 clips (18%), the dose was smaller than 13.0 Gy indicating that locally the gap was larger than 5 mm. In 22 clips the dose was between 13.0 and 15.0 Gy. Conclusion: The time needed for IOBT could be reduced by using standard plans, but the treatment dose was on average 4.5 % lower than the prescribed 10 Gy (p < 0.0001). A significant dose reduction of 8% was seen in the central dose point while the dose at the corners was unaltered. A too low dose was found in 18% of the clip locations. Clinical practise will have to prove if these small dose deviations influence the clinical outcome. 66

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Outcome after intraoperative HDR brachytherapy (IOBT) for close or positive margins in patients with locally advanced or recurrent rectum cancer J. Nuyttens 1, /. Ko/kman-Deur/oo 1, F. Ferenschi/d 1, M. Vermaas 1, W. Graveland 2, P. Hanssens 1, P. Levendag 1 t Erasmus MC-Daniel Den Hoed Cancer Center, Radiotherapy, Rotterdam, The Netherlands 2Erasmus MC-Daniel Den Hoed Cancer Center, Statistics, Rotterdam, The Netherlands Introduction: Local failure of locally advanced or recurrent rectum cancer after conventional treatment is high. An analysis was made to determine the role of intraoperative HDR brachytherapy (IOBT) in reducing local failures. Methods and materials: Between 1997 and 2000, 40 patients were treated with external beam radiotherapy (EBRT), surgery and IOBT. After exclusion of metastatic patients, 37 patients are left. Eighteen patients had Primary Locally Advanced Rectum Cancer (PLARC), 19 Recurrent Rectum Cancer (RRC). Six patients received an EBRT dose of 25-30 Gy, 31 patients 50 Gy. One tow anterior resection, 21 abdominoperineal (APR) and 15 abdominosacral resections (ASR) were performed. The Flexible lntraoperative Template (FIT) developed at our department is a 5 mm thick silicon pad with 1-cm spaced parallel catheters running through the center. Treatment planning was performed using standard geometries present in the treatment planning system. A dose of 10 Gy was delivered at 1 cm depth from the template surface. IOBT was only administered if resection margins were equal or less than 2 mm. The resection margin was judged on frosen section. According to the final pathology report, positive margins were found in 18 patients, negative margins in 19 patients. No patients were lost in follow up. The mean follow up of surviving patients is 3.3 years (2-5.3 years). Results: Overall, 12 patients (33%) had a local recurrence, five (14%) were IOBT in-field. Four tOBT in-field failures were diagnosed in patients with recurrent disease. The mean time to the local recurrence was 3.7 years. The time to local failure was significantly different for PLARC vs. RRC (mean 4.3 vs. 2.8 years, p=0.042) and for patients with APR vs. ASR (mean 4.2 vs 2.7 years, p=0.043). The 2 year actuarial local failure rate was 23% for negative margins and 26% for positive margins. The mean overall survival was 3.3 years. Two patients (5%) died of local disease, seventeen