- Email: [email protected]
ADAPTIVE RADIOTHERAPY TO TREATMENT RESPONSE
M ONDAY, AUGUST 31, 2009
S YMPOSIUM
S 21
also be minimized using a robust design in the intensity modulated arc delivery.
head and neck cancer patients. Methodological aspects and pitfalls with the use of multimodality images will be highlighted.
50 speaker
52 speaker
ADAPTIVE RADIOTHERAPY TO TREATMENT RESPONSE X. Geets1 , P. Castadot2 , J. Lee1 , V. Grégoire1 1 UCL-C LINIQUES U NIVERSITAIRES S AINT L UC, Department of Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium 2 UCL C LINIQUES U NIV. S T.L UC, Department of Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium
MRI IMAGES OF THE ANATOMY OF THE AXILLARY AND SUPRACLAVICULAR REGION IN TREATMENT POSITION FOR ADJUVANT RADIATION TREATMENT OF BREAST CANCER C. I. Kiricuta1 1 S T. V INCENZ H OSPITAL, Radiation Oncology, Limburg, Germany Abstract not received.
Introduction: the recent progresses performed in imaging, computational and technological fields bring new opportunities to achieve high precision radiation dose delivery. However, IMRT requires a particular attention to the target delineation to avoid inadequate dosage to TVs/OARs. In this context, the biological information provided by PET might advantageously complete CT-Scan to refine the target delineation in HNSCC, while re-imaging the tumor during the course of fractionated radiotherapy might account for the constantly changing anatomy and tumor shape.Material/Methods: the intrinsic characteristics of PET, including the blur effect and the high level of noise, make the accurate detection of the tumor edges arduous. In this context, we developed specific tools, i.e. edge-preserving filters for denoising and deconvolution algorithms for deblurring that allowed gradient peaks detection. Our gradient-based segmentation method has been validated on phantom and patient materials, and proved to be more accurate than thresholdbased approaches. With this tool in hand, we designed a proof of concept study on adaptive ART including 10 patients with locally-advanced HNSCC. The patients were imaged by CT-Scan, MRI and FDG-PET, before the treatment start, but also during radiotherapy at weeks 2, 3, 4 and 5. The GTV was delineated manually on CT and MRI images, and by the gradient-based method on FDG-PET images. Results: the volume analysis showed that the use of PET provided significantly smaller TVs than morphological imaging modalities, while a significant tumor shrinkage (about 50%) has been observed on images acquired after 45 Gy, whatever the imaging modality used. Resulting FDG-PET based and adaptive planning using SIB IMRT with helical tomotherapy reduced the high-dose irradiated volumes by 15-35% compared to conventional pre-treatment CT-based planning. More recently, we demonstrated that replanning could compensate for dosimetric degradations caused by anatomic modifications during treatment.Conclusion: combining highly conformal radiation techniques and refinement in target volumes definition by means of PET and re-imaging opens avenue for dose escalation strategies. However, biological and physical issues still remains to be dealt with, and further clinical trials still have to address the safety and the clinical impact of such approaches on patient outcome.
Imaging for target delineation, tumour sites 51 speaker WHICH IMAGING IS NEEDED FOR PLANNING H&N SQUAMOUS CELL CARCINOMA V. Grégoire1 1 UCL C LINIQUES U NIV. S T.L UC, Radiation Oncology Dept. and Center for Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium
The ultimate objective of radiotherapy is to achieve a high percentage of locoregional control with a low incidence of morbidity, hence directly impacting on the overall survival and the quality of life of patients. In this framework, one of the first steps in the radiotherapy planning process is to precisely select and delineate the target volumes (i.e. the tumor) and the surrounding normal tissues potentially responsible for treatment morbidity if irradiated at a too high dose. For a long time, CT has been used as the reference imaging modality as it can also be used for dose calculation (taking into account the Hounsfield units, which are surrogates of tissue density). This requires that the image acquisition is performed in treatment position, thus with the patients immobilized on a flat tabletop. In pharyngo-laryngeal tumors, our group has shown that MRI did not brink any advantage over CT neither for the delineation accuracy, nor for the inter-observer variability. On the contrary, more recently, several groups including our, have shown that providing the images are acquired, reconstructed and segmented in a proper way, FDG-PET improved the delineation of pharyngo-laryngeal tumor volumes. This improvement translated into an improvement in dose distribution, i.e. a lower dose was delivered to the surrounding normal tissues. This finding opens the way for a possible increase in the dose prescription -thus potentially increasing the probability of loco-regional control- without increasing the dose to the surrounding normal tissues. Furthermore, the use of PET with other tracers imaging biological pathways involved in radiation response (e.g. cell proliferation, tumor hypoxia) open a new avenue to specifically deliver an extra dose to the PET-positive area, i.e. the so-called "dose painting" approach.After a short description of the radiotherapy processes, the lecture will focus on the usefulness of the various anatomic and functional imaging modalities for radiotherapy treatment of
53 speaker TARGET VOLUME DEFINITION FOR STAGE I NSCLC: SINGLE 4D CT SCAN VS. ONE STANDARD VS. SIX STANDARD CT SCANS D. De Ruysscher1 , G. Bosmans2 , M. Öllers2 , S. Wanders2 , A. van Baardwijk2 , B. Reymen2 , J. Borger2 , A. Dekker3 , P. Lambin4 1 M AASTRICHT R ADIATION O NCOLOGY (MAASTRO), GROW, U NIVERSITY H OSPITAL M AASTRICHT, Maastricht, Netherlands 2 MAASTRO CLINIC, Maastricht, Netherlands 3 MAASTRO C LINIC, Maastricht, Netherlands 4 U NIVERSITY H OSPITAL M AASTRICHT, M AASTRICHT U NIVERSITY, MAASTRO CLINIC, GROW, Maastricht, Netherlands
Historically, patients with stage I-II non-small cell lung cancer (NSCLC) who were for medical reasons such as COPD and/ or cardiac co-morbidity inoperable, were treated with conventional radiotherapy. Typical, radiation doses of 60-70 Gy, delivered in 30-35 fractions in 6-7 weeks were delivered. However, local tumor control was in general only 30-40 % with 5-year survival rates of about 20 %. Stereotactic Body Radiation (SBRT), in which a few very high doses of radiation (e.g. 60 Gy delivered in 3 fractions) are delivered to small tumors that are located in selected lung regions, has increased local tumor control to over 85 % with less than 5 % of patients experiencing important side effects. SBRT requires highly specialized radiotherapy techniques, equipment, including 4D respiration correlated CT-scans. Indeed, an accurate individualized 3D definition of target volumes is a prerequisite because of the high doses per fraction and steep dose gradients in SBRT. Because CT is a fast imaging technique, a single CT will capture the tumor at only one phase of the respiration. If the tumor is not at its central position when it is imaged, a systematic error is introduced possibly resulting in a geographic miss. Moreover, the motion of the tumor with respiration causes an intra-fractional random error, which cannot be estimated on a single CT. The systematic error has a much larger contribution to the internal margin than the random error. Respiration correlated CT (RCCT) give information about tumor motion during respiration. Including this information in treatment planning may lead to more optimal treatment plans, avoiding geographic miss and minimizing margins. Although a slow CT reduced the Internal Target Volume (ITV) the most, tumor delineation is inaccurate due to the blurring of the lesion at the edges. In addition, the Clinical Target Volume (CTV) coverage using slow CT may result in under-dosage.Delineation of the ITV on 6 or 10 respiratory phases is adequate, but very labor-intensive and is prone to delineation errors and variability. Half- or mid-ventilation CT, combined with individual anisotropic margins, is the most suitable method for the ITV definition of lung tumors. This method is easy (only one phase), the tumor is clearly visible (no blurring due to motion) and the reduced margin is adequate. 54 speaker IMPLEMENTATION OF FUNCTIONAL IMAGING IN THE TREATMENT OF PLANNING PROCESS U. Nestle1 1 U NIVERSITÄTSKLINIKUM F REIBURG, Klinik für Strahlenheilkunde, Freiburg, Germany
In recent years, several functional imaging modalities like PET, SPECT and new MRI techniques have arrived in routine diagnostic imaging. Beyond the properties of anatomical imaging, these methods offer complementary information on various aspects of tumor biology. Their value has been proven e.g. for the diagnosis of malignant spread, staging, monitoring and evaluation of response. Due to the possibility of imaging tumors and/or their subvolumes, functional imaging methods are of interest for radiation therapy planning. However, while for diagnostic purposes factors like the probability of malignancy in a questionable lesion or the impact of imaging findings on surgical decision making are focussed, the questions posed in radiation therapy planning are different. Firstly, there is the topic of "where is the edge of the tumor" going along with a whole bunch of technical issues, starting with image reconstruction, coregistration and data transfer, ending up with segmentation and GTV-contouring. Secondly, there is the question of radiooncological concepts, which may have to be changed in the light of the new
S YMPOSIUM
S 21
also be minimized using a robust design in the intensity modulated arc delivery.
head and neck cancer patients. Methodological aspects and pitfalls with the use of multimodality images will be highlighted.
50 speaker
52 speaker
ADAPTIVE RADIOTHERAPY TO TREATMENT RESPONSE X. Geets1 , P. Castadot2 , J. Lee1 , V. Grégoire1 1 UCL-C LINIQUES U NIVERSITAIRES S AINT L UC, Department of Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium 2 UCL C LINIQUES U NIV. S T.L UC, Department of Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium
MRI IMAGES OF THE ANATOMY OF THE AXILLARY AND SUPRACLAVICULAR REGION IN TREATMENT POSITION FOR ADJUVANT RADIATION TREATMENT OF BREAST CANCER C. I. Kiricuta1 1 S T. V INCENZ H OSPITAL, Radiation Oncology, Limburg, Germany Abstract not received.
Introduction: the recent progresses performed in imaging, computational and technological fields bring new opportunities to achieve high precision radiation dose delivery. However, IMRT requires a particular attention to the target delineation to avoid inadequate dosage to TVs/OARs. In this context, the biological information provided by PET might advantageously complete CT-Scan to refine the target delineation in HNSCC, while re-imaging the tumor during the course of fractionated radiotherapy might account for the constantly changing anatomy and tumor shape.Material/Methods: the intrinsic characteristics of PET, including the blur effect and the high level of noise, make the accurate detection of the tumor edges arduous. In this context, we developed specific tools, i.e. edge-preserving filters for denoising and deconvolution algorithms for deblurring that allowed gradient peaks detection. Our gradient-based segmentation method has been validated on phantom and patient materials, and proved to be more accurate than thresholdbased approaches. With this tool in hand, we designed a proof of concept study on adaptive ART including 10 patients with locally-advanced HNSCC. The patients were imaged by CT-Scan, MRI and FDG-PET, before the treatment start, but also during radiotherapy at weeks 2, 3, 4 and 5. The GTV was delineated manually on CT and MRI images, and by the gradient-based method on FDG-PET images. Results: the volume analysis showed that the use of PET provided significantly smaller TVs than morphological imaging modalities, while a significant tumor shrinkage (about 50%) has been observed on images acquired after 45 Gy, whatever the imaging modality used. Resulting FDG-PET based and adaptive planning using SIB IMRT with helical tomotherapy reduced the high-dose irradiated volumes by 15-35% compared to conventional pre-treatment CT-based planning. More recently, we demonstrated that replanning could compensate for dosimetric degradations caused by anatomic modifications during treatment.Conclusion: combining highly conformal radiation techniques and refinement in target volumes definition by means of PET and re-imaging opens avenue for dose escalation strategies. However, biological and physical issues still remains to be dealt with, and further clinical trials still have to address the safety and the clinical impact of such approaches on patient outcome.
Imaging for target delineation, tumour sites 51 speaker WHICH IMAGING IS NEEDED FOR PLANNING H&N SQUAMOUS CELL CARCINOMA V. Grégoire1 1 UCL C LINIQUES U NIV. S T.L UC, Radiation Oncology Dept. and Center for Molecular Imaging and Experimental Radiotherapy, Brussels, Belgium
The ultimate objective of radiotherapy is to achieve a high percentage of locoregional control with a low incidence of morbidity, hence directly impacting on the overall survival and the quality of life of patients. In this framework, one of the first steps in the radiotherapy planning process is to precisely select and delineate the target volumes (i.e. the tumor) and the surrounding normal tissues potentially responsible for treatment morbidity if irradiated at a too high dose. For a long time, CT has been used as the reference imaging modality as it can also be used for dose calculation (taking into account the Hounsfield units, which are surrogates of tissue density). This requires that the image acquisition is performed in treatment position, thus with the patients immobilized on a flat tabletop. In pharyngo-laryngeal tumors, our group has shown that MRI did not brink any advantage over CT neither for the delineation accuracy, nor for the inter-observer variability. On the contrary, more recently, several groups including our, have shown that providing the images are acquired, reconstructed and segmented in a proper way, FDG-PET improved the delineation of pharyngo-laryngeal tumor volumes. This improvement translated into an improvement in dose distribution, i.e. a lower dose was delivered to the surrounding normal tissues. This finding opens the way for a possible increase in the dose prescription -thus potentially increasing the probability of loco-regional control- without increasing the dose to the surrounding normal tissues. Furthermore, the use of PET with other tracers imaging biological pathways involved in radiation response (e.g. cell proliferation, tumor hypoxia) open a new avenue to specifically deliver an extra dose to the PET-positive area, i.e. the so-called "dose painting" approach.After a short description of the radiotherapy processes, the lecture will focus on the usefulness of the various anatomic and functional imaging modalities for radiotherapy treatment of
53 speaker TARGET VOLUME DEFINITION FOR STAGE I NSCLC: SINGLE 4D CT SCAN VS. ONE STANDARD VS. SIX STANDARD CT SCANS D. De Ruysscher1 , G. Bosmans2 , M. Öllers2 , S. Wanders2 , A. van Baardwijk2 , B. Reymen2 , J. Borger2 , A. Dekker3 , P. Lambin4 1 M AASTRICHT R ADIATION O NCOLOGY (MAASTRO), GROW, U NIVERSITY H OSPITAL M AASTRICHT, Maastricht, Netherlands 2 MAASTRO CLINIC, Maastricht, Netherlands 3 MAASTRO C LINIC, Maastricht, Netherlands 4 U NIVERSITY H OSPITAL M AASTRICHT, M AASTRICHT U NIVERSITY, MAASTRO CLINIC, GROW, Maastricht, Netherlands
Historically, patients with stage I-II non-small cell lung cancer (NSCLC) who were for medical reasons such as COPD and/ or cardiac co-morbidity inoperable, were treated with conventional radiotherapy. Typical, radiation doses of 60-70 Gy, delivered in 30-35 fractions in 6-7 weeks were delivered. However, local tumor control was in general only 30-40 % with 5-year survival rates of about 20 %. Stereotactic Body Radiation (SBRT), in which a few very high doses of radiation (e.g. 60 Gy delivered in 3 fractions) are delivered to small tumors that are located in selected lung regions, has increased local tumor control to over 85 % with less than 5 % of patients experiencing important side effects. SBRT requires highly specialized radiotherapy techniques, equipment, including 4D respiration correlated CT-scans. Indeed, an accurate individualized 3D definition of target volumes is a prerequisite because of the high doses per fraction and steep dose gradients in SBRT. Because CT is a fast imaging technique, a single CT will capture the tumor at only one phase of the respiration. If the tumor is not at its central position when it is imaged, a systematic error is introduced possibly resulting in a geographic miss. Moreover, the motion of the tumor with respiration causes an intra-fractional random error, which cannot be estimated on a single CT. The systematic error has a much larger contribution to the internal margin than the random error. Respiration correlated CT (RCCT) give information about tumor motion during respiration. Including this information in treatment planning may lead to more optimal treatment plans, avoiding geographic miss and minimizing margins. Although a slow CT reduced the Internal Target Volume (ITV) the most, tumor delineation is inaccurate due to the blurring of the lesion at the edges. In addition, the Clinical Target Volume (CTV) coverage using slow CT may result in under-dosage.Delineation of the ITV on 6 or 10 respiratory phases is adequate, but very labor-intensive and is prone to delineation errors and variability. Half- or mid-ventilation CT, combined with individual anisotropic margins, is the most suitable method for the ITV definition of lung tumors. This method is easy (only one phase), the tumor is clearly visible (no blurring due to motion) and the reduced margin is adequate. 54 speaker IMPLEMENTATION OF FUNCTIONAL IMAGING IN THE TREATMENT OF PLANNING PROCESS U. Nestle1 1 U NIVERSITÄTSKLINIKUM F REIBURG, Klinik für Strahlenheilkunde, Freiburg, Germany
In recent years, several functional imaging modalities like PET, SPECT and new MRI techniques have arrived in routine diagnostic imaging. Beyond the properties of anatomical imaging, these methods offer complementary information on various aspects of tumor biology. Their value has been proven e.g. for the diagnosis of malignant spread, staging, monitoring and evaluation of response. Due to the possibility of imaging tumors and/or their subvolumes, functional imaging methods are of interest for radiation therapy planning. However, while for diagnostic purposes factors like the probability of malignancy in a questionable lesion or the impact of imaging findings on surgical decision making are focussed, the questions posed in radiation therapy planning are different. Firstly, there is the topic of "where is the edge of the tumor" going along with a whole bunch of technical issues, starting with image reconstruction, coregistration and data transfer, ending up with segmentation and GTV-contouring. Secondly, there is the question of radiooncological concepts, which may have to be changed in the light of the new