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171 oral Clinical and dosimetric risk factors of radiation pneumonitis in 3D conformal irradiation of thoracic cancer
$68 Wednesday, 17 September 2003
this planning study dose-volume histogram (DVH) data and normal tissue complication probability (NTCP) predictions for intestine and rectum were compared for different combinations of clinically applied margin widths and fractionation schedules in bladder irradiation. Material and Methods: Normal tissue dose distributions in fifteen bladder cancer patients treated with radical CRT were studied retrospectively, using standard three-field (Ant/Laterals) and four-field (Ant/Post/Laterals) beam configurations as model set-ups. The impact of margin width on the normal tissue dose distribution was initially evaluated using DVH data. NTCP modelling was used to compare the impact of choice of margin size and fractionation schedule. The analysis included treatment margin combinations of 1.0 cm isotropic (narrow margins) and 1.2-2.0 cm non-isotropic (wide margins) and fractionation schedule alternatives of 52.5 Gy/20, 55 Gy/20, 57.5 Gy/20 and 64 Gy/32. Results: Using wide margins, the volumes of intestine and rectum receiving high doses increased by factors of approximately two and four, respectively, compared to using narrow margins. Similar factors between wide and narrow margins were also found for intestine and rectum NTCPs at the different fractionation alternatives, but the impact of margin size depended on the volume effect expressed by the NTCP model parameters. However, using standard NTCP parameters, the choice of margins and fractionation schedule had a similar impact on intestine NTCP predictions, while for the rectum, the choice of margin had a greater impact than the choice of fractionation. For a given choice of margin, the intestine and rectum NTCP predictions using 55 Gy/20 and 64 Gy/32 fractionation schedules were comparable. For clinics using narrow margins and a fractionation of 52.5 Gy/20, the NTCP modelling suggested that a moderate dose escalation (to 55 Gy/20 or 64 Gy/32) or changing to wide margins had a similar effect on the intestine and rectum NTCP predictions. Conclusion: This modelling study of bladder irradiation suggested that the choice of margins was as important as the choice of fractionation in terms of intestine and rectum DVH parameters and NTCP predictions. The 55 Gy/20 and 64 Gy/32 fractionation schedules appeared to be comparable in terms of intestine and rectum NTCP predictions. 171
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Clinical and dosimetric risk factors of radiation pneumonitis in 3D conformal irradiation of thoracic cancer A. Foqliata 1, T. Rancati2, . L. Cozzi 1, J. Bemier 3 l oncology Institute of Southern Switzerland, Medical Physics, Bellinzona, Switzerland 2University of Milan, Dept. of Physics, Milan, Italy 30ncology Institute of Southern Switzerland, Radiation Oncology, Bellinzona, Switzerland Objective: to investigate the relationship between a number of clinical and dosimetric risk factors and the development of radiation pneumonitis (RP) in patients (PTs) treated with thoracic irradiation. Materials and Methods: records of 80 consecutive thoracic PTs irradiated at dose>40 Gy with full 3D dosimetry data and a follow-up time of >6 months from start of treatment were retrospectively reviewed. RP was scored on the basis of SWOG toxicity criteria and was considered a complication when grade II (use of steroids required). Gender, age, surgery, chemotherapy and presence of chronic obstructive oulmonary disease (COPD) were considered as clinical parameters. Dosimetric factors including mean lung dose (Dm), % of lung (Vx) receiving > x Gy, minumum dose (Dy) at a fixed % (Dy%) of lung volume and normal tissue complication probability (NTCP) values were also analysed. DVH data and NTCP values were collected for the ipsilateral lung. Results: 13 PTs (16.3%) had RP. Sex, age, many dosimetric parameters (Dm, V25, V35, D20, D30, D40) and NTCP were significantly associated with RP in univariate analysis. No significant correlation was found between RP and surgery, chemotherapy and COPD. Multivariate analysis (overall p=0.0077) revealed that age (p=0.079) and D30 (p=0.04) were the main risk factors for RP. Conclusions: DVH based parameters (mainly D30) revealed to be good predictors of RP, and they can be used in clinical practice to recognize PTs belonging to high-risk group for RP or to perform dose escalation for PTs in the low-risk group. Conclusion: (1) Statistical results on D20 < 40 Gy and D30< 42 Gy seem to point out that lung has 20-30% of its volume acting as a sort of "functional reserve". This percentage of volume can be irradiated at relatively high doses without having high risk of RP (RP risk ? 0-3% in this study). (2) D20< 35 Gy: patients with this characteristic could be considered ad low risk group (0 RPs in this study) allowing the option for dose escalation, (3) Patients with D20 > 54 Gy are identified as the high risk group (30% RP in this study). [n our internal code of practice these patients should require
Proffered papers
higher conformation degree of RT plan. 172
oral
Patient involvement in prostate cancer treatment decisions H. Huizencla 1, J.J. van ToI-Geerdink 1, P.F.M. Stalmeier 2, P.C.M. Paskerde Jong 3, E.N.J.T. van Lin 1, C.G. Verhoef4, A.L. Hoffmann 1, J.W.H. Leer 1,4, W.A.J. van Daal 1 1University Medical Centre Nijmegen, Radiotherapy, Nijmegen, The Netherlands 2University Medical Centre Nijmegen, Medical Technology Assessment, Nijmegen, The Netherlands 3University Medical Centre Nijmegen, Epidemiology, Nijmegen, The Netherlands 4Amhems Radiotherapeutic Institute, Amhem, The Netherlands introduction: The process of radiotherapy treatment planning involves choices between dose to the tumor and dose to organs at risk. Usually these choices are implemented in treatment protocols or are made explicitly by the physician. Two reasons have boosted research about possible explicit involvement of patients in these choices. Firstly, physicians are legally obliged now to provide information so patients can be involved in their own treatment choices. Secondly, the development of IMRT requires a more explicit definition of treatment objectives and constraints in treatment planning. Research goals are to find out whether patients want to be involved in treatment choices and whether they accept treatment outcome better when they have been involved explicitly in these choices. Research has been started involving prostate cancer patients. Method~: To provide adequate information to patients on treatment outcome in terms of treatment control and morbidity, a systematic review of literature has been carried out. Also, the treatment results in our institutions were analysed retrospectively. Further, a standardised patient interview and follow-up schedule was defined and tested. Starting May 2003, the best possible information will be presented to prostate patients about treatment outcome of a "74 Gy" and a "70 Gy" 3D conformal therapy treatment. Then, they will be asked whether they want to be involved in the choice between "74 Gy" and "70 Gy"i If not, the physician will make the choice for them. The patients will be followed by means of questionnaires until six months after completion of the treatment in order to assess their medical and psychological well-being. Earlv results: The systematic review, including 37 studies published in the last 10 years, clearly shows the effects of increased dose in the 70 to 78 Gy dose range on tumor control (-1.2%/Gy), GI late morbidity (-1.5 °/o/Gy, for a 7 mm margin at the prostate-rectum interface), GU late morbidity (-0.75%/Gy) and sexual dysfunction (-2.5°/o/Gy). A relevant dependence was found in GI late morbidity as function of CTV-PTV margin at the prostate rectum interface. An effect due to increased attention to positioning (e.g. immobilisation, EPID, use of gold markers, use of rectal balloons) could not be derived from literature. This complicates the information to the patients since it is generally expected that improved positioning of patients along with IMRT will further enlarge the therapeutic window.
IMRT: P L A N N I N G A N D O P T I M I S A T I O N 173 oral A novel linear programming approach to fluence map o p t i m i z a t i o n for intensity modulated radiation therapy treatment planning
J.F. Demosev*. H.E. Romeijn*, R.K. Ahuja*, A. Kumar*, J.G. Li* *Department of Industrial and Systems Engineering, University of Fledda, Gainesville, Florida 32611-6595 **Department of Radiation Oncology, University of Florida, Gainesville, Fled da 32610-0385 [email protected], [email protected], [email protected], [email protected], [email protected] We present a novel linear programming (LP) based approach for efficiently solving the intensity modulated radiation therapy (IMRT) fluence-map optimization (FMO) problem to global optimality. Our model overcomes the apparent limitations of a linear-programming approach by approximating any convex objective function by a piecewise linear convex function. This approach allows us to retain the flexibility offered by general convex objective functions, while allowing us to formulate the FMO problem as a LP. In addition, a novel type of partial-volume constraints that bound the tail averages of the differential dose-volume histograms of structures are imposed
this planning study dose-volume histogram (DVH) data and normal tissue complication probability (NTCP) predictions for intestine and rectum were compared for different combinations of clinically applied margin widths and fractionation schedules in bladder irradiation. Material and Methods: Normal tissue dose distributions in fifteen bladder cancer patients treated with radical CRT were studied retrospectively, using standard three-field (Ant/Laterals) and four-field (Ant/Post/Laterals) beam configurations as model set-ups. The impact of margin width on the normal tissue dose distribution was initially evaluated using DVH data. NTCP modelling was used to compare the impact of choice of margin size and fractionation schedule. The analysis included treatment margin combinations of 1.0 cm isotropic (narrow margins) and 1.2-2.0 cm non-isotropic (wide margins) and fractionation schedule alternatives of 52.5 Gy/20, 55 Gy/20, 57.5 Gy/20 and 64 Gy/32. Results: Using wide margins, the volumes of intestine and rectum receiving high doses increased by factors of approximately two and four, respectively, compared to using narrow margins. Similar factors between wide and narrow margins were also found for intestine and rectum NTCPs at the different fractionation alternatives, but the impact of margin size depended on the volume effect expressed by the NTCP model parameters. However, using standard NTCP parameters, the choice of margins and fractionation schedule had a similar impact on intestine NTCP predictions, while for the rectum, the choice of margin had a greater impact than the choice of fractionation. For a given choice of margin, the intestine and rectum NTCP predictions using 55 Gy/20 and 64 Gy/32 fractionation schedules were comparable. For clinics using narrow margins and a fractionation of 52.5 Gy/20, the NTCP modelling suggested that a moderate dose escalation (to 55 Gy/20 or 64 Gy/32) or changing to wide margins had a similar effect on the intestine and rectum NTCP predictions. Conclusion: This modelling study of bladder irradiation suggested that the choice of margins was as important as the choice of fractionation in terms of intestine and rectum DVH parameters and NTCP predictions. The 55 Gy/20 and 64 Gy/32 fractionation schedules appeared to be comparable in terms of intestine and rectum NTCP predictions. 171
oral
Clinical and dosimetric risk factors of radiation pneumonitis in 3D conformal irradiation of thoracic cancer A. Foqliata 1, T. Rancati2, . L. Cozzi 1, J. Bemier 3 l oncology Institute of Southern Switzerland, Medical Physics, Bellinzona, Switzerland 2University of Milan, Dept. of Physics, Milan, Italy 30ncology Institute of Southern Switzerland, Radiation Oncology, Bellinzona, Switzerland Objective: to investigate the relationship between a number of clinical and dosimetric risk factors and the development of radiation pneumonitis (RP) in patients (PTs) treated with thoracic irradiation. Materials and Methods: records of 80 consecutive thoracic PTs irradiated at dose>40 Gy with full 3D dosimetry data and a follow-up time of >6 months from start of treatment were retrospectively reviewed. RP was scored on the basis of SWOG toxicity criteria and was considered a complication when grade II (use of steroids required). Gender, age, surgery, chemotherapy and presence of chronic obstructive oulmonary disease (COPD) were considered as clinical parameters. Dosimetric factors including mean lung dose (Dm), % of lung (Vx) receiving > x Gy, minumum dose (Dy) at a fixed % (Dy%) of lung volume and normal tissue complication probability (NTCP) values were also analysed. DVH data and NTCP values were collected for the ipsilateral lung. Results: 13 PTs (16.3%) had RP. Sex, age, many dosimetric parameters (Dm, V25, V35, D20, D30, D40) and NTCP were significantly associated with RP in univariate analysis. No significant correlation was found between RP and surgery, chemotherapy and COPD. Multivariate analysis (overall p=0.0077) revealed that age (p=0.079) and D30 (p=0.04) were the main risk factors for RP. Conclusions: DVH based parameters (mainly D30) revealed to be good predictors of RP, and they can be used in clinical practice to recognize PTs belonging to high-risk group for RP or to perform dose escalation for PTs in the low-risk group. Conclusion: (1) Statistical results on D20 < 40 Gy and D30< 42 Gy seem to point out that lung has 20-30% of its volume acting as a sort of "functional reserve". This percentage of volume can be irradiated at relatively high doses without having high risk of RP (RP risk ? 0-3% in this study). (2) D20< 35 Gy: patients with this characteristic could be considered ad low risk group (0 RPs in this study) allowing the option for dose escalation, (3) Patients with D20 > 54 Gy are identified as the high risk group (30% RP in this study). [n our internal code of practice these patients should require
Proffered papers
higher conformation degree of RT plan. 172
oral
Patient involvement in prostate cancer treatment decisions H. Huizencla 1, J.J. van ToI-Geerdink 1, P.F.M. Stalmeier 2, P.C.M. Paskerde Jong 3, E.N.J.T. van Lin 1, C.G. Verhoef4, A.L. Hoffmann 1, J.W.H. Leer 1,4, W.A.J. van Daal 1 1University Medical Centre Nijmegen, Radiotherapy, Nijmegen, The Netherlands 2University Medical Centre Nijmegen, Medical Technology Assessment, Nijmegen, The Netherlands 3University Medical Centre Nijmegen, Epidemiology, Nijmegen, The Netherlands 4Amhems Radiotherapeutic Institute, Amhem, The Netherlands introduction: The process of radiotherapy treatment planning involves choices between dose to the tumor and dose to organs at risk. Usually these choices are implemented in treatment protocols or are made explicitly by the physician. Two reasons have boosted research about possible explicit involvement of patients in these choices. Firstly, physicians are legally obliged now to provide information so patients can be involved in their own treatment choices. Secondly, the development of IMRT requires a more explicit definition of treatment objectives and constraints in treatment planning. Research goals are to find out whether patients want to be involved in treatment choices and whether they accept treatment outcome better when they have been involved explicitly in these choices. Research has been started involving prostate cancer patients. Method~: To provide adequate information to patients on treatment outcome in terms of treatment control and morbidity, a systematic review of literature has been carried out. Also, the treatment results in our institutions were analysed retrospectively. Further, a standardised patient interview and follow-up schedule was defined and tested. Starting May 2003, the best possible information will be presented to prostate patients about treatment outcome of a "74 Gy" and a "70 Gy" 3D conformal therapy treatment. Then, they will be asked whether they want to be involved in the choice between "74 Gy" and "70 Gy"i If not, the physician will make the choice for them. The patients will be followed by means of questionnaires until six months after completion of the treatment in order to assess their medical and psychological well-being. Earlv results: The systematic review, including 37 studies published in the last 10 years, clearly shows the effects of increased dose in the 70 to 78 Gy dose range on tumor control (-1.2%/Gy), GI late morbidity (-1.5 °/o/Gy, for a 7 mm margin at the prostate-rectum interface), GU late morbidity (-0.75%/Gy) and sexual dysfunction (-2.5°/o/Gy). A relevant dependence was found in GI late morbidity as function of CTV-PTV margin at the prostate rectum interface. An effect due to increased attention to positioning (e.g. immobilisation, EPID, use of gold markers, use of rectal balloons) could not be derived from literature. This complicates the information to the patients since it is generally expected that improved positioning of patients along with IMRT will further enlarge the therapeutic window.
IMRT: P L A N N I N G A N D O P T I M I S A T I O N 173 oral A novel linear programming approach to fluence map o p t i m i z a t i o n for intensity modulated radiation therapy treatment planning
J.F. Demosev*. H.E. Romeijn*, R.K. Ahuja*, A. Kumar*, J.G. Li* *Department of Industrial and Systems Engineering, University of Fledda, Gainesville, Florida 32611-6595 **Department of Radiation Oncology, University of Florida, Gainesville, Fled da 32610-0385 [email protected], [email protected], [email protected], [email protected], [email protected] We present a novel linear programming (LP) based approach for efficiently solving the intensity modulated radiation therapy (IMRT) fluence-map optimization (FMO) problem to global optimality. Our model overcomes the apparent limitations of a linear-programming approach by approximating any convex objective function by a piecewise linear convex function. This approach allows us to retain the flexibility offered by general convex objective functions, while allowing us to formulate the FMO problem as a LP. In addition, a novel type of partial-volume constraints that bound the tail averages of the differential dose-volume histograms of structures are imposed