- Email: [email protected]
147 oral MULTICENTRE STUDY OF MRI-GUIDED BRACHYTHERAPY TREATMENT PLANNING: COMPARISON AMONG TANDEM OVOID APPLICATOR USERS
M ONDAY, M AY 9, 2011
therapy. Such a culture, open and non-punitive, should be actively encouraged through regular multidisciplinary meetings to promote inter-professional communication while respecting and understanding the different roles and responsibilities of individuals. Communication among staff members is essential for all aspects of the radiotherapy process, since mistakes may be made because of lack of adequate communication, incorrect information, or poor understanding of correct information. As a concluding remark it should be acknowledged that education and training is not the only contributing factor to improving safety in radiotherapy. Nevertheless, the different approaches to acquisition of knowledge, skills and competencies are certainly a fundamental pillar supporting patient safety.
P ROFFERED PAPER
S 55
Proffered paper GEC Proffered Papers 3: Cervix Cancer 147 oral MULTICENTRE STUDY OF MRI-GUIDED BRACHYTHERAPY TREATMENT PLANNING: COMPARISON AMONG TANDEM OVOID APPLICATOR USERS C. Nomden1 , A. de Leeuw1 , E. Van Limbergen2 , M. De Brabandere2 , A. Nulens2 , R. Nout3 , M. Laman3 , M. Ketelaars3 , B. Reniers4 , L. Lutgens4 , I. M. Jürgenliemk-Schulz1 1 U NIVERSITY M EDICAL C ENTER U TRECHT, Radiation Oncology, Utrecht, Netherlands 2 U NIVERSITY H OSPITAL G ASTHUISBERG, Radiation Oncology, Leuven, Belgium 3 L EIDEN U NIVERSITY M EDICAL C ENTER (LUMC), Clinical Oncology, Leiden, Netherlands 4 MAASTRO CLINIC, Radiation Oncology, Maastricht, Netherlands
Purpose: To compare different MRI-guided brachytherapy (BT) treatment planning methods for cervical cancer in 4 centres that use the tandem-ovoid applicator. Materials: For this study we selected 4 patients from the Utrecht clinical database that are included in the EMBRACE study. High risk clinical target volumes (HR-CTV) and organs at risk (OAR) were delineated according to GEC-ESTRO recommendations and applicator reconstructions were performed. Volumes of HR-CTV were 19.5, 31.9 33.8, and 68.0 cm3 . Three of the 4 patients were clinically treated with the intracavitary/interstitial (IC/IS) approach, and one intracavitary alone.Four centres (2 using PDR and 2 HDR) with different historical BT background performed treatment planning on these data sets. Each centre created for each of the 4 patients the following plans: an institutional standard (STD) plan normalised to point A, an optimised MRI-guided treatment plan without (OPT) and one with use of interstitial needles (OPTN). One centre had no experience with the IC/IS approach and therefore did not generate the OPTN treatment plans. The aim for the D90 HR-CTV (dose given to 90% of the high risk volume) was 85Gy EQD2 for all treatment plans. The dose constraints for the OAR’s (bladder, rectum, sigmoid and bowel) were 90, 75, 75 and 75Gy EQD2, respectively. All centres kept their institutional ’soft constraints’ for treatment planning.We analysed and compared DVH-parameters, source loading patterns, dose distributions and ’soft constraints’. Results: The D90 HR-CTV values derived from the STD plans were similar while variations in OAR’s dose were noticed. Optimisation resulted in smaller variations in the OAR doses while by adding interstitial needles the variation increased. Optimised plans with needles showed in all cases higher D90 HR-CTV than without needles but the variation among the centres increased. The source loading patterns (SLP) of the standard treatment plans varied between the 4 centres. After optimisation the SLP were more comparable. However, the dwell weights chosen for the source positions varied, resulting in different contributions of the applicator parts to the dose distribution. Figure 1 shows an example of one of the patients. The ratio between the D2cc OAR and the D90 HR-CTV, decreased from STD over OPT to OPTN. A lower ratio represents the favourable situation of a lower dose to the OAR and a higher dose to the HR-CTV.
Conclusions: MRI guided treatment planning results in more comparable DVH parameters than standard planning. The relative contributions of the tandem, ovoids and needles were quite different between the centres. It is remarkable that although similar dose objectives were applied and obtained for D90 HR-CTV and D2cc OARs the dose and source time distributions are quite different. This study induced discussions on source loading patterns, dose distributions and other soft constraints, which in the future may lead to more comparable treatment approaches.
therapy. Such a culture, open and non-punitive, should be actively encouraged through regular multidisciplinary meetings to promote inter-professional communication while respecting and understanding the different roles and responsibilities of individuals. Communication among staff members is essential for all aspects of the radiotherapy process, since mistakes may be made because of lack of adequate communication, incorrect information, or poor understanding of correct information. As a concluding remark it should be acknowledged that education and training is not the only contributing factor to improving safety in radiotherapy. Nevertheless, the different approaches to acquisition of knowledge, skills and competencies are certainly a fundamental pillar supporting patient safety.
P ROFFERED PAPER
S 55
Proffered paper GEC Proffered Papers 3: Cervix Cancer 147 oral MULTICENTRE STUDY OF MRI-GUIDED BRACHYTHERAPY TREATMENT PLANNING: COMPARISON AMONG TANDEM OVOID APPLICATOR USERS C. Nomden1 , A. de Leeuw1 , E. Van Limbergen2 , M. De Brabandere2 , A. Nulens2 , R. Nout3 , M. Laman3 , M. Ketelaars3 , B. Reniers4 , L. Lutgens4 , I. M. Jürgenliemk-Schulz1 1 U NIVERSITY M EDICAL C ENTER U TRECHT, Radiation Oncology, Utrecht, Netherlands 2 U NIVERSITY H OSPITAL G ASTHUISBERG, Radiation Oncology, Leuven, Belgium 3 L EIDEN U NIVERSITY M EDICAL C ENTER (LUMC), Clinical Oncology, Leiden, Netherlands 4 MAASTRO CLINIC, Radiation Oncology, Maastricht, Netherlands
Purpose: To compare different MRI-guided brachytherapy (BT) treatment planning methods for cervical cancer in 4 centres that use the tandem-ovoid applicator. Materials: For this study we selected 4 patients from the Utrecht clinical database that are included in the EMBRACE study. High risk clinical target volumes (HR-CTV) and organs at risk (OAR) were delineated according to GEC-ESTRO recommendations and applicator reconstructions were performed. Volumes of HR-CTV were 19.5, 31.9 33.8, and 68.0 cm3 . Three of the 4 patients were clinically treated with the intracavitary/interstitial (IC/IS) approach, and one intracavitary alone.Four centres (2 using PDR and 2 HDR) with different historical BT background performed treatment planning on these data sets. Each centre created for each of the 4 patients the following plans: an institutional standard (STD) plan normalised to point A, an optimised MRI-guided treatment plan without (OPT) and one with use of interstitial needles (OPTN). One centre had no experience with the IC/IS approach and therefore did not generate the OPTN treatment plans. The aim for the D90 HR-CTV (dose given to 90% of the high risk volume) was 85Gy EQD2 for all treatment plans. The dose constraints for the OAR’s (bladder, rectum, sigmoid and bowel) were 90, 75, 75 and 75Gy EQD2, respectively. All centres kept their institutional ’soft constraints’ for treatment planning.We analysed and compared DVH-parameters, source loading patterns, dose distributions and ’soft constraints’. Results: The D90 HR-CTV values derived from the STD plans were similar while variations in OAR’s dose were noticed. Optimisation resulted in smaller variations in the OAR doses while by adding interstitial needles the variation increased. Optimised plans with needles showed in all cases higher D90 HR-CTV than without needles but the variation among the centres increased. The source loading patterns (SLP) of the standard treatment plans varied between the 4 centres. After optimisation the SLP were more comparable. However, the dwell weights chosen for the source positions varied, resulting in different contributions of the applicator parts to the dose distribution. Figure 1 shows an example of one of the patients. The ratio between the D2cc OAR and the D90 HR-CTV, decreased from STD over OPT to OPTN. A lower ratio represents the favourable situation of a lower dose to the OAR and a higher dose to the HR-CTV.
Conclusions: MRI guided treatment planning results in more comparable DVH parameters than standard planning. The relative contributions of the tandem, ovoids and needles were quite different between the centres. It is remarkable that although similar dose objectives were applied and obtained for D90 HR-CTV and D2cc OARs the dose and source time distributions are quite different. This study induced discussions on source loading patterns, dose distributions and other soft constraints, which in the future may lead to more comparable treatment approaches.