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149 From 3D-conformal radiotherapy to IMRT: fact or fiction?
S70 Tuesday, October 26, 2004
Symposia Prostate cancer 147 Prostate imaging for radiotherapy planning
G. Vi//eirs~, G. De Meer/eeF ~Ghent University Hospital, Department of Radiology, Gent, Belgium 2Ghent University Hospital, Department of Radiotherapy, Gent, Belgium With the advent of conformal radiotherapy and especially intensity modulated radiotherapy for prostate cancer, it has become increasingly important to delineate the target volume (prostate + seminal vesicles) as accurate as possible. With computed tomography (CT), the delineated volume is likely to be imprecise to a certain extent, because of the low organ discriminating power based solely on differences of attenuation coefficients and the restriction to acquire images only in the transverse plane. On the other hand, magnetic resonance imaging (MRI) offers superb soft tissue contrast on T2-weighted images and allows direct multiplanar image acquisition without loss of spatial resolution. It can show the internal prostatic anatomy, prostatic margins, and the extent of prostatic tumors in much more detail than CT images, leading to more accurate delineations of both prostate and critical structures, with improved target coverage. Furthermore, dynamic imaging techniques such as magnetic resonance spectroscopy and dynamic contrast-enhanced Tl-weighted imaging are able to increase the tumor detection rate and enhance the definition of subtargets within the prostate, which could be treated to higher doses. 148 Improving accuracy of prostate
X. Art(qnan Abstract not received 149 From 3D-conformal radiotherapy to IMRT: fact or fiction ?
P. Mainqon Centre Georges-Frangois Leclerc, Department of Radiotherapy, Dijon, France The outcome after the treatment of localized prostate cancer mainly depends on the attainment of local tumor control. The value of prognostic factors such as tumor stage, grading, Gleason score, pre-treatment PSA level and the number of positive biopsy course is well established. Dose escalation trials have clearly demonstrated that increasing the overall radiation dose leads to a higher tumor control probability. Simultaneously an increasing dose to the prostate induces a higher rate of acute and late side effects. The development and use of new radiotherapy techniques, especially 3D Conformal Radiotherapy (3D-CRT) or Intensity Modulated Radiotherapy (IMRT) allows a safe application of high doses of external beam radiotherapy without increasing toxicity. Thus, it appears that dose escalation to the prostate is limited to the dose burden to organs at risk. IMRT of prostate cancer patients has become an issue of major interest in radiotherapy. An increasing number of radiotherapy departments are currently implementing IMRT into routine work or are on the way to do so. It is now demonstrated that the implementation of IMRT to clinical routine is feasible but requires an accurate quality assurance program concerning verification of individual IMRT plans and a clinical QA. Quality assurance in IMRT treatments at first
consists of clinical quality assurance as regards selection criteria, strict definition of patient immobilization and set up verification. The acquired volume during CT planning has to be recorded under strict procedures followed by each individual patient. The definition of the clinical target volume and the PTV has to be in accordance with our knowledge of prostate movement, risks of extension of the tumor outside the capsular, probability of invasion of seminal vesicles. During IMRT treatment, dose volume constraints have to be established according to the literature data on acute and late toxicity. Treatment verification is an important part of the accuracy of the treatment delivery. It could be performed using an electronic portal imaging device and now accuracy could be improved by using ultra-sound based daily prostate repositioning. Some studies are currently under the way to evaluate internal prostate markers and prostate movements using high resolution amorphal silicone EPID. The physical quality assurance is based on a regular machine related quality assurance procedures, dosimetric planned verification and dosimetric field by field verification and independent monitor unit checks. At present, the introduction of iMRT allows to reduce the dose delivered to the rectum and the bulb of the penis decreasing the probability of late complications related to the GI tract and to the potency of the patient.
Head and neck cancer: consequences of combined chemo-radiation 150 Optimization of radiotherapy in chemo-radiation protocols
K.K. Ang U. T. M.D. Anderson Cancer Center, Department of Radiotherapy, Houston, TX, U.S.A. Intensive basic and clinical investigations have advanced our understanding of the biology of head and neck carcinoma (HNC) and have improved the treatment outcome. Collectively, phase III clinical trials demonstrated conclusively the superiority of a few biologically sound radiotherapy fractionation regimens and a number of combinations of radiation with chemotherapy in obtaining a higher local-regional t u m o r control probability and, less uniformly, in yielding a better overall survival rate relative to conventional radiotherapy alone. However, these altered fractionations and combined modality regimens were also found to increase acute side effects and, in some radiationchemotherapy schedules, more severe late morbidity as well. Consequently, there is ongoing debate as to which altered fractionation or radiation-chemotherapy regimen should be considered as the current standard-of-care for various stages of HNC. In addition, progress in radiation planning and delivery technology, e.g., intensity modulated radiation therapy (IMRT), has opened the possibility to better confine radiation dose to the tumor and its path of potential microscopic spread and thereby reducing high dose exposure to surrounding normal tissues. There is general optimism that proper integration of such conformal technology would lead to further improvement in therapy outcome but the best approach to accomplishing this goal is still being investigated. The objectives of this paper are to: 1) briefly summarize the data of recently published clinical trials with the emphasis on combined therapy regimens; 2) highlight radiotherapy aspects needing careful consideration in planning a combined modality therapy; and 3) address a number of current and future research directions.
Symposia Prostate cancer 147 Prostate imaging for radiotherapy planning
G. Vi//eirs~, G. De Meer/eeF ~Ghent University Hospital, Department of Radiology, Gent, Belgium 2Ghent University Hospital, Department of Radiotherapy, Gent, Belgium With the advent of conformal radiotherapy and especially intensity modulated radiotherapy for prostate cancer, it has become increasingly important to delineate the target volume (prostate + seminal vesicles) as accurate as possible. With computed tomography (CT), the delineated volume is likely to be imprecise to a certain extent, because of the low organ discriminating power based solely on differences of attenuation coefficients and the restriction to acquire images only in the transverse plane. On the other hand, magnetic resonance imaging (MRI) offers superb soft tissue contrast on T2-weighted images and allows direct multiplanar image acquisition without loss of spatial resolution. It can show the internal prostatic anatomy, prostatic margins, and the extent of prostatic tumors in much more detail than CT images, leading to more accurate delineations of both prostate and critical structures, with improved target coverage. Furthermore, dynamic imaging techniques such as magnetic resonance spectroscopy and dynamic contrast-enhanced Tl-weighted imaging are able to increase the tumor detection rate and enhance the definition of subtargets within the prostate, which could be treated to higher doses. 148 Improving accuracy of prostate
X. Art(qnan Abstract not received 149 From 3D-conformal radiotherapy to IMRT: fact or fiction ?
P. Mainqon Centre Georges-Frangois Leclerc, Department of Radiotherapy, Dijon, France The outcome after the treatment of localized prostate cancer mainly depends on the attainment of local tumor control. The value of prognostic factors such as tumor stage, grading, Gleason score, pre-treatment PSA level and the number of positive biopsy course is well established. Dose escalation trials have clearly demonstrated that increasing the overall radiation dose leads to a higher tumor control probability. Simultaneously an increasing dose to the prostate induces a higher rate of acute and late side effects. The development and use of new radiotherapy techniques, especially 3D Conformal Radiotherapy (3D-CRT) or Intensity Modulated Radiotherapy (IMRT) allows a safe application of high doses of external beam radiotherapy without increasing toxicity. Thus, it appears that dose escalation to the prostate is limited to the dose burden to organs at risk. IMRT of prostate cancer patients has become an issue of major interest in radiotherapy. An increasing number of radiotherapy departments are currently implementing IMRT into routine work or are on the way to do so. It is now demonstrated that the implementation of IMRT to clinical routine is feasible but requires an accurate quality assurance program concerning verification of individual IMRT plans and a clinical QA. Quality assurance in IMRT treatments at first
consists of clinical quality assurance as regards selection criteria, strict definition of patient immobilization and set up verification. The acquired volume during CT planning has to be recorded under strict procedures followed by each individual patient. The definition of the clinical target volume and the PTV has to be in accordance with our knowledge of prostate movement, risks of extension of the tumor outside the capsular, probability of invasion of seminal vesicles. During IMRT treatment, dose volume constraints have to be established according to the literature data on acute and late toxicity. Treatment verification is an important part of the accuracy of the treatment delivery. It could be performed using an electronic portal imaging device and now accuracy could be improved by using ultra-sound based daily prostate repositioning. Some studies are currently under the way to evaluate internal prostate markers and prostate movements using high resolution amorphal silicone EPID. The physical quality assurance is based on a regular machine related quality assurance procedures, dosimetric planned verification and dosimetric field by field verification and independent monitor unit checks. At present, the introduction of iMRT allows to reduce the dose delivered to the rectum and the bulb of the penis decreasing the probability of late complications related to the GI tract and to the potency of the patient.
Head and neck cancer: consequences of combined chemo-radiation 150 Optimization of radiotherapy in chemo-radiation protocols
K.K. Ang U. T. M.D. Anderson Cancer Center, Department of Radiotherapy, Houston, TX, U.S.A. Intensive basic and clinical investigations have advanced our understanding of the biology of head and neck carcinoma (HNC) and have improved the treatment outcome. Collectively, phase III clinical trials demonstrated conclusively the superiority of a few biologically sound radiotherapy fractionation regimens and a number of combinations of radiation with chemotherapy in obtaining a higher local-regional t u m o r control probability and, less uniformly, in yielding a better overall survival rate relative to conventional radiotherapy alone. However, these altered fractionations and combined modality regimens were also found to increase acute side effects and, in some radiationchemotherapy schedules, more severe late morbidity as well. Consequently, there is ongoing debate as to which altered fractionation or radiation-chemotherapy regimen should be considered as the current standard-of-care for various stages of HNC. In addition, progress in radiation planning and delivery technology, e.g., intensity modulated radiation therapy (IMRT), has opened the possibility to better confine radiation dose to the tumor and its path of potential microscopic spread and thereby reducing high dose exposure to surrounding normal tissues. There is general optimism that proper integration of such conformal technology would lead to further improvement in therapy outcome but the best approach to accomplishing this goal is still being investigated. The objectives of this paper are to: 1) briefly summarize the data of recently published clinical trials with the emphasis on combined therapy regimens; 2) highlight radiotherapy aspects needing careful consideration in planning a combined modality therapy; and 3) address a number of current and future research directions.