- Email: [email protected]
SP-0406: Adaptive strategies to account for functional changes
S215 ESTRO 36 _______________________________________________________________________________________________ used in nuclear medicine, and as will be described in this talk, also to provide a novel method to monitor externalbeam RT. CLI is becoming a well-established method for preclinical in vivo small animal optical imaging and has been also applied to humans for example to image a patient treated with 131-I [2]. A very recent approach is the use of CLI for the analysis of ex vivo fresh tumor specimens removed during neurosurgery [3]. From the radiotherapy side there has been considerable interest in the possible use of CLI to monitor externalbeam radiation therapy. The main dosimetric parameters that could be measured are the percent depth dose (PDD) and the lateral dose profile of the radiation beam. It has been hypothesized that these parameters can be directly measured by imaging the CR induced in a water phantom as a surrogate of the dose. In the literature it has been shown that due to the anisotropy of the CR emission some differences arise between the CR-derived and the true dose profiles, these differences in the PDD and lateral dose profile can be taken into account by using correction factors derived from Monte Carlo simulations [4]. A more practical approach to reduce the effect of Cerenkov emission anisotropy is adding a CR-excitable fluorophore to the water in the phantom, the addition of a fluorophore allows more accurate estimation of the PPD [5]. The use of CLI for real-time portal imaging during CyberKnife radiation therapy was also investigated by irradiating a water tank phantom. Imaging at 30 frames per second was acquired showing that CLI is a feasible tool to image dynamic and static objects [6]. An interesting development is the use of CR to visualize in real time the dose delivery during radiation therapy [7], more precisely it has been shown that it is possible to visualize the surface dose during the treatment. In conclusion, the use of CLI in the RT field could lead to a novel approaches to perform QA and real time in vivo dosimetry References [1] Jelley JV 1958 Cerenkov Radiation and Its Applications (London: Pergamon) [2] Spinelli, AE, Ferdeghini, M, Cavedon, C, Zivelonghi, E, Calandrino, R, Fenzi A. et al, First human Cerenkography. J Biomed Opt. 2013;18:020502. [3] Spinelli AE, Schiariti MP, Grana CM, Ferrari M, Cremonesi M, Boschi F. Cerenkov and radioluminescence imaging of brain tumor specimens during neurosurgery.J Biomed Opt. 2016 1;21(5):50502. [4] Glaser AK, Davis SC, McClatchy DM, Zhang R, Pogue B.W. Gladstone, D.J. Projection imaging of photon beams by the Cerenkov effect. Med Phys. 2013;40:012101. [5] Glaser AK, Davis SC, Voigt WH, Zhan R, Pogue BW, Gladstone DJ Projection imaging of photon beams using Čerenkov-excited fluorescence. Phys Med Biol. 2013;58:601–619. [6] Roussakis Y, Zhang R, Heyes G, Webster G, Mason S, Green S, Pogue B, Dehghani H. Real-time Cherenkov emission portal imaging during CyberKnife® radiotherapy. Phys Med Biol. 2015 Nov 21;60(22):N41925. [7] Jarvis LA, Zhan R, Gladstone DJ, Jiang S, Hitchcock W, Friedman O.D. et al . Cherenkov video imaging allows for the first visualization of radiation therapy in real time. Int J Radiat Oncol Biol Phys. 2014;89:615–622. Symposium: Adaptive radiotherapy (both anatomical and ‘functional’ changes) SP-0404 Development and Clinical Implementation of Image Registration and Dose Accumulation
K. Brock1 1 MD Anderson Cancer Center, Imaging Physics, Houston, USA Image registration is challenging in simple cases of deformable tissues. In the presence of anatomical and functional changes, these challenges can substantially increase. This presentation will evaluate the translation of standard deformable image registration techniques to challenging cases of anatomical and function response. Limitations of the techniques in the adaptive scenario will be discussed and validation techniques will be described. Although all registration techniques have uncertainties, once understood and quantified, the clinical application of these registration techniques can often improve the treatment in the adaptive radiotherapy treatment paradigm. One of the primary uses of deformable image registration for adaptive radiotherapy is dose accumulation, including the accumulation of dose assessed on each treatment fraction as well as the propagation of the initially planned dose onto the adaptive or replanning image. This process generates a wealth of data that can overwhelm a clinical process. Strategies will be discussed for distilling this data down into meaningful data that can be clinically evaluated. This presentation will also illustrate dose accumulation workflows that are clinically feasible as well as the use of deformable registration for dose propagation between an initial and adaptive planning image. Objectives for this presentation include: 1. Describing techniques and limitations of image registration in the presence of anatomical and functional changes 2. Addressing the question: how accurate is accurate enough for clinical use 3. Illustrating a workflow for dose accumulation that is clinically feasible 4. Strategies for reporting dose accumulation results SP-0405 Adaptive strategies to account for anatomical changes J.J. Sonke1 1 Netherlands Cancer Institute, Radiotherapy department, Amsterdam, The Netherlands Geometric uncertainties limit the precision and accuracy of radiotherapy. In room imaging techniques are now readily available to reimage the patient prior to and during treatment. Typically, these images are used to reposition the patient and thus minimize target misalignment. Anatomical changes, however, frequently occur during treatment but cannot be accurately corrected for using a couch shift. Adaptive radiotherapy, on the other hand, utilizes an imaging based feedback loop to adjust the treatment plan and thus has to potential to account for such anatomical changes. In this presentation, the magnitude and frequency of anatomical changes will be exemplified and various adaptive protocols will be described. Finally, current challenges and future perspective of adaptive strategies to account for anatomical changes will be discussed. SP-0406 Adaptive strategies to account for functional changes I. Toma-Dasu1 1 Karolinska Institutet, Medical Radiation Physics, Stockholm, Sweden The progress and technological development of functional and molecular techniques for imaging tumours has offered the possibility of redefining the target in radiation therapy and devising the treatment in an innovative manner accounting for relevant biological information on metabolic, biochemical and physiological factors known to
S216 ESTRO 36 _______________________________________________________________________________________________ be related to poor treatment response. Thus, dose painting approaches have been proposed based on the hypothesis that local recurrence is related to resistant foci not eradicated by the currently prescribed doses, which might however be controlled by delivering nonhomogeneous dose distributions targeting specific tumour phenotypes related to local control or risk of relapse after (chemo)radiotherapy. Clinical implementation of dose painting, however, is not a trivial task and the success cannot be guaranteed as there are several potential challenges and limitations related to the imaging techniques, the underlying radiobiological aspects and the current techniques for delivering the heterogeneous dose distributions. This talk will present a paradigm shift from focusing on the radiobiological dose prescription, such as in dose painting approaches, to biologically adapted radiation therapy, based on tumour responsiveness assessed with functional imaging. Thus, the general idea is to use functional information from advanced imaging modalities for the assessment of the tumour response early on during the course of the treatment followed by the adaptation of the treatment for the patients for which poor response is predicted. A previous study showing that the early response to treatment of NSCLC patients can be evaluated by stratifying the patients in good and poor responders based on calculations of the effective radiosensitivity derived from two FDG-PET scans taken before the treatment and during the second week of radiotherapy will be presented. Complementing studies on the feasibility of effective radiosensitivity calculations for H&N cancer patients as well as the identification of the optimal window during the treatment for assessing the effective radiosensitivity will also be presented. For the patient classified as poor responders, the distribution of the effective radiosensitivity displayed as a map of response overlapping onto the GTV could be used for guiding adaptive planning approaches. Thus, the method to be presented in this talk would allow the delineation of the sub-volumes expressing lack of response, hence the sub-volumes that should receive a dose boost as adaptive treatment based on functional imaging. Several strategies for treatment adaptation, including photon and proton irradiation, will be considered. This is an extremely novel approach to response assessment and treatment adaptation that opens the way for true treatment individualisation in radiation therapy. Symposium: Focus on lung cancer: What a radiotherapy department should offer their patients SP-0407 PET/CT artefacts for RT planning A. Santos1 1 Hospital Cuf Descobertas- S.A., Nuclear Medicine Department, Lisboa, Portugal Nuclear Medicine, along with PET/CT technology has been playing an important role in the detection, staging and follow-up of lung cancer. The therapeutic approach to lung cancer can vary, depending on the staging of the tumour, being Radiotherapy one of the most important of the available treatments. The association of PET/CT to radiotherapy planning has a synergic effect that will benefit the patient. Nuclear Medicine Technologists (NMT) that perform PET/CT must be aware of the numerous artefacts and pitfalls that can influence the acquired images and the results of the diagnostic procedure. The equipment must have its quality standards assured, radiopharmacy aspects must be covered, the patient should be correctly prepared and also perform all stages of the procedure accordingly. Anyhow, artefacts and pitfalls can randomly occur and this is why it is so important to have theorical knowledge and practical skills in order to correctly identify the artefacts and correct it
when required. In addition, the active participation of the Radiotherapy technologists (RTT) in the multidisciplinary team surely increases the quality of the results. NMT benefit from the valuable inputs from RTT, since these professionals are specialists in radiotherapy patient positioning, and will be the common factor between PET/CT acquisition and radiotherapy treatment. Also, RTT commonly have a prior relation with the patient and this might play an important role in the patient welfare. The humanization of patient care, along with the state of the art of the technology, are the focus of the multidisciplinary team that surrounds the patient. SP-0408 ART in lung cancer: when and for whom? P. Berkovic1 1 C.H.U. - Sart Tilman, Radiotherapy department, Liège, Belgium Lung cancer is the most common cause of cancer death worldwide [1]. Non-small cell lung cancer (NSCLC) accounts for 80 – 85% of all lung cancers of which about 30% are locally advanced (LA) at diagnosis [2]. Although concurrent chemoradiotherapy (cCRT) improves survival compared to sequential one (sCRT) [3], there remains room for improvement in the treatment of LA-NSCLC. Within the radiotherapy component, several possible treatment strategies were investigated, such as altered fractionation and/or dose escalation. However, dose escalation is severely hampered by normal tissue toxicity [4] and can lead to deleterious results when used without taking patient-, tumor- and treatment characteristics into account. This hurdle can be overcome by patientindividualized treatment approaches such as individualized dose-escalation using fixed dose constraints or adapting the treatment-fields to the shrinking tumor. However, adaptive radiotherapy (ART) is time consuming and it is not clear which patient is eligible or what the optimal time point for ART should be. Technical advances, such as intensity-modulated radiotherapy (IMRT) and tumor motion strategies, may further improve the therapeutic ratio. To reach full potential, these strategies imply the use of image-guided radiotherapy (IGRT), e.g. by using a cone-beam computed tomography (CBCT). The latter also allows monitoring tumor volume or -position changes over the treatment course. In this lecture we will address both anatomical- and especially tumor volume changes during chemoradiation and analyse potential predictive factors of volume and dosimetric parameter changes, as well as the potential gain to organs at risk (OARs) while maintaining target volume coverage. Furthermore, the optimal implementation strategy regarding selection of patients (who) and timing of imaging/replanning (when) will be discussed with an overview of the results, from a physician’s perspective. References: [1] Ferlay J et al. Estimates of worldwide burden of cancer in 2008 : GLOBOCAN 2008. Int J Cancer 2010 ;127: 2893 – 917. [2] Peters S et al. Metastatic non-small-cell lung cancer (NSCLC): ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up . Ann Oncol 2012 ; 23(Suppl 7) : vii56 – 64. [3] Auperin A et al. Meta-analysis of concomitant versus sequential radiochemotherapy in locally advanced nonsmall-cell lung cancer . J Clin Oncol 2010 ; 28 : 2181 – 90. [4] Bradley J. A review of radiation dose escalation trials for non-small cell lung cancer within the Radiation Therapy Oncology Group . Semin Oncol 2005 ; 32 : S111 – 3. SP-0409 Improvements in physics, DIBH in lung M. Josipovic1 1 The Finsen Center - Rigshospitalet, Copenhagen, Denmark
K. Brock1 1 MD Anderson Cancer Center, Imaging Physics, Houston, USA Image registration is challenging in simple cases of deformable tissues. In the presence of anatomical and functional changes, these challenges can substantially increase. This presentation will evaluate the translation of standard deformable image registration techniques to challenging cases of anatomical and function response. Limitations of the techniques in the adaptive scenario will be discussed and validation techniques will be described. Although all registration techniques have uncertainties, once understood and quantified, the clinical application of these registration techniques can often improve the treatment in the adaptive radiotherapy treatment paradigm. One of the primary uses of deformable image registration for adaptive radiotherapy is dose accumulation, including the accumulation of dose assessed on each treatment fraction as well as the propagation of the initially planned dose onto the adaptive or replanning image. This process generates a wealth of data that can overwhelm a clinical process. Strategies will be discussed for distilling this data down into meaningful data that can be clinically evaluated. This presentation will also illustrate dose accumulation workflows that are clinically feasible as well as the use of deformable registration for dose propagation between an initial and adaptive planning image. Objectives for this presentation include: 1. Describing techniques and limitations of image registration in the presence of anatomical and functional changes 2. Addressing the question: how accurate is accurate enough for clinical use 3. Illustrating a workflow for dose accumulation that is clinically feasible 4. Strategies for reporting dose accumulation results SP-0405 Adaptive strategies to account for anatomical changes J.J. Sonke1 1 Netherlands Cancer Institute, Radiotherapy department, Amsterdam, The Netherlands Geometric uncertainties limit the precision and accuracy of radiotherapy. In room imaging techniques are now readily available to reimage the patient prior to and during treatment. Typically, these images are used to reposition the patient and thus minimize target misalignment. Anatomical changes, however, frequently occur during treatment but cannot be accurately corrected for using a couch shift. Adaptive radiotherapy, on the other hand, utilizes an imaging based feedback loop to adjust the treatment plan and thus has to potential to account for such anatomical changes. In this presentation, the magnitude and frequency of anatomical changes will be exemplified and various adaptive protocols will be described. Finally, current challenges and future perspective of adaptive strategies to account for anatomical changes will be discussed. SP-0406 Adaptive strategies to account for functional changes I. Toma-Dasu1 1 Karolinska Institutet, Medical Radiation Physics, Stockholm, Sweden The progress and technological development of functional and molecular techniques for imaging tumours has offered the possibility of redefining the target in radiation therapy and devising the treatment in an innovative manner accounting for relevant biological information on metabolic, biochemical and physiological factors known to
S216 ESTRO 36 _______________________________________________________________________________________________ be related to poor treatment response. Thus, dose painting approaches have been proposed based on the hypothesis that local recurrence is related to resistant foci not eradicated by the currently prescribed doses, which might however be controlled by delivering nonhomogeneous dose distributions targeting specific tumour phenotypes related to local control or risk of relapse after (chemo)radiotherapy. Clinical implementation of dose painting, however, is not a trivial task and the success cannot be guaranteed as there are several potential challenges and limitations related to the imaging techniques, the underlying radiobiological aspects and the current techniques for delivering the heterogeneous dose distributions. This talk will present a paradigm shift from focusing on the radiobiological dose prescription, such as in dose painting approaches, to biologically adapted radiation therapy, based on tumour responsiveness assessed with functional imaging. Thus, the general idea is to use functional information from advanced imaging modalities for the assessment of the tumour response early on during the course of the treatment followed by the adaptation of the treatment for the patients for which poor response is predicted. A previous study showing that the early response to treatment of NSCLC patients can be evaluated by stratifying the patients in good and poor responders based on calculations of the effective radiosensitivity derived from two FDG-PET scans taken before the treatment and during the second week of radiotherapy will be presented. Complementing studies on the feasibility of effective radiosensitivity calculations for H&N cancer patients as well as the identification of the optimal window during the treatment for assessing the effective radiosensitivity will also be presented. For the patient classified as poor responders, the distribution of the effective radiosensitivity displayed as a map of response overlapping onto the GTV could be used for guiding adaptive planning approaches. Thus, the method to be presented in this talk would allow the delineation of the sub-volumes expressing lack of response, hence the sub-volumes that should receive a dose boost as adaptive treatment based on functional imaging. Several strategies for treatment adaptation, including photon and proton irradiation, will be considered. This is an extremely novel approach to response assessment and treatment adaptation that opens the way for true treatment individualisation in radiation therapy. Symposium: Focus on lung cancer: What a radiotherapy department should offer their patients SP-0407 PET/CT artefacts for RT planning A. Santos1 1 Hospital Cuf Descobertas- S.A., Nuclear Medicine Department, Lisboa, Portugal Nuclear Medicine, along with PET/CT technology has been playing an important role in the detection, staging and follow-up of lung cancer. The therapeutic approach to lung cancer can vary, depending on the staging of the tumour, being Radiotherapy one of the most important of the available treatments. The association of PET/CT to radiotherapy planning has a synergic effect that will benefit the patient. Nuclear Medicine Technologists (NMT) that perform PET/CT must be aware of the numerous artefacts and pitfalls that can influence the acquired images and the results of the diagnostic procedure. The equipment must have its quality standards assured, radiopharmacy aspects must be covered, the patient should be correctly prepared and also perform all stages of the procedure accordingly. Anyhow, artefacts and pitfalls can randomly occur and this is why it is so important to have theorical knowledge and practical skills in order to correctly identify the artefacts and correct it
when required. In addition, the active participation of the Radiotherapy technologists (RTT) in the multidisciplinary team surely increases the quality of the results. NMT benefit from the valuable inputs from RTT, since these professionals are specialists in radiotherapy patient positioning, and will be the common factor between PET/CT acquisition and radiotherapy treatment. Also, RTT commonly have a prior relation with the patient and this might play an important role in the patient welfare. The humanization of patient care, along with the state of the art of the technology, are the focus of the multidisciplinary team that surrounds the patient. SP-0408 ART in lung cancer: when and for whom? P. Berkovic1 1 C.H.U. - Sart Tilman, Radiotherapy department, Liège, Belgium Lung cancer is the most common cause of cancer death worldwide [1]. Non-small cell lung cancer (NSCLC) accounts for 80 – 85% of all lung cancers of which about 30% are locally advanced (LA) at diagnosis [2]. Although concurrent chemoradiotherapy (cCRT) improves survival compared to sequential one (sCRT) [3], there remains room for improvement in the treatment of LA-NSCLC. Within the radiotherapy component, several possible treatment strategies were investigated, such as altered fractionation and/or dose escalation. However, dose escalation is severely hampered by normal tissue toxicity [4] and can lead to deleterious results when used without taking patient-, tumor- and treatment characteristics into account. This hurdle can be overcome by patientindividualized treatment approaches such as individualized dose-escalation using fixed dose constraints or adapting the treatment-fields to the shrinking tumor. However, adaptive radiotherapy (ART) is time consuming and it is not clear which patient is eligible or what the optimal time point for ART should be. Technical advances, such as intensity-modulated radiotherapy (IMRT) and tumor motion strategies, may further improve the therapeutic ratio. To reach full potential, these strategies imply the use of image-guided radiotherapy (IGRT), e.g. by using a cone-beam computed tomography (CBCT). The latter also allows monitoring tumor volume or -position changes over the treatment course. In this lecture we will address both anatomical- and especially tumor volume changes during chemoradiation and analyse potential predictive factors of volume and dosimetric parameter changes, as well as the potential gain to organs at risk (OARs) while maintaining target volume coverage. Furthermore, the optimal implementation strategy regarding selection of patients (who) and timing of imaging/replanning (when) will be discussed with an overview of the results, from a physician’s perspective. References: [1] Ferlay J et al. Estimates of worldwide burden of cancer in 2008 : GLOBOCAN 2008. Int J Cancer 2010 ;127: 2893 – 917. [2] Peters S et al. Metastatic non-small-cell lung cancer (NSCLC): ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up . Ann Oncol 2012 ; 23(Suppl 7) : vii56 – 64. [3] Auperin A et al. Meta-analysis of concomitant versus sequential radiochemotherapy in locally advanced nonsmall-cell lung cancer . J Clin Oncol 2010 ; 28 : 2181 – 90. [4] Bradley J. A review of radiation dose escalation trials for non-small cell lung cancer within the Radiation Therapy Oncology Group . Semin Oncol 2005 ; 32 : S111 – 3. SP-0409 Improvements in physics, DIBH in lung M. Josipovic1 1 The Finsen Center - Rigshospitalet, Copenhagen, Denmark