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58 Spot scanning proton therapy: Treatment planning and treatment verification
Invited Speakers
Mar ch 12 - 15
sometimes done automatically as a part of treatment plan optimization, may easily invalidate the principle of similarity. 58 SPOT SCANNING PROTON THERAPY: PLANNING A N D TREATMENT V E R I F I C A T I O N
TREATMENT
A.J. Lomax, F. Albertini, T. Boehringer, A. Bols, M. Bosshardt, A. Coray, G. Goitein, S. Lin, E. Pedroni, M. Stenecker, J. Verwey Department of Radiation Medicine, Paul Scherrer Institute, Switzerland Objective: Proton therapy provides many challenges to the treatment planning and verification of such treatments in the clinical routines. Here we describe some of the issues in these areas that we have addressed. Material and Methods: In the past 9 years we have learnt a number of things about the planning process. In particular, we have looked into the effects of different number of fields on the quality of proton plans for head and neck cases, studied the possibilities of reducing the number of applied Bragg peaks per field and also the possible detrimental effects of density heterogeneities and how to possibly avoid them. In terms of verification, we have introduced a field specific verification regime which was applied to all fields in the first 6 years, and is now applied only to more complex cases. An interesting area to be investigated however is the verification of the range of the protons in the patient, an area where proton radiography could be of great use. Results: For certain indications, there appears to be little advantage to increasing the number of fields beyond three, and have found that there is considerable scope for reducing the number of Bragg peaks delivered per field. A heterogeneity index has also been introduced into the planning system for predicting poor angles of approach to the tumour, and this has been found to be of some use for improving the homogeneity of dose to the tumour volume. Our field specific verification regime has shown that our delivery system can reliably and accurately deliver complex fields, but there is considerable work to be done in developing methods for the direct veification of range in the patient and for extending the verifications to multi-dimensional measurements. Conclusion: 9 years of experience has shown that dynami proton therapy can be delivered accurately and safely. However, there is much interesting work in the planning and verification of such treatments still to be done.
59 ADVANCED-TECHNOLOGY R A D I A T I O N THERAPY I N THE MANAGEMENT OF BONE AND SOFT TISSUE SARCOMAS
T.F. Delaney Massachusetts General Hospiatl, Boston, USA Objective: For patients with sarcoma, radiotherapy can be used as neoadjuvant, adjuvant, or primary therapy, depending upon the site and type of sarcoma, the surgical approach, and the efficacy of chemotherapy. Material and methods: Review of the current status of advanced technology radiation therapy in the management of bone and soft tissue sarcomas. Results: Advances in radiation therapy technology permit improved treatment for patients with bone and soft ~issue sarcomas. Most promising are intensity modulated radiation therapy (IMRT), proton beam or other charged particle radiation therapy, brachytherapy, and intra-operative radiation therapy. These deliver highly conformal radiation doses to complex target volumes near critical normal tissues. When combined with refinements in tumor target definition with MRI scan and PET/CT imaging, more precise delivery of radiation to the tumor while sparing adjacent normal tissues is possible. Intensity-modulated radiation therapy (IMRT) uses modifications in the intensity of the photon beam from a linear accelerator across the irradiated fields to enhance dose conformation in 3-dimensions. For proton beam radiation therapy, the nuclei of hydrogen atoms are accelerated in cyclotrons or synchrotrons, extracted and transported to treatment rooms where the proton beam undergoes a series of modifications (spreading, modulation and shaping) that conform the dose in a particular patient to the tumor target. Recent technical developments in hospital-based proton facilities with rotational gantries have generated considerable enthusiasm for the use of proton beams in radiation therapy.
$21
Comparable dose distributions to the tumor target itself can be achieved with intensity modulated photons or conformal proton beams. Because of their charge and mass, however, protons have a finite range and no dose is delivered distal to the desired target. In addition, dose proximal to the target is lower with protons and, up to certain depths in tissue, the penumbra of the beam is sharper. Proton beam therapy thus provides a means to reduce the volume of irradiated normal tissue and as well as the dose received by normal tissue. This may permit higher doses to the tumor and achieve a higher tumor control probability without increasing the frequency or severity of radiation-related morbidity. Additionally, the more conformal treatment volumes of proton therapy will result in reduced frequency and severity of co-morbidity between radiation and chemotherapy, thus improving tolerance of the patient to therapy and avoiding toxicity-induced interruptions in treatment that might compromise its efficacy. Interest in heavier charged particles has focused primarily on carbon ions. Still considered experimental, carbon ions have a greater relative biologic effect than protons; the pivotal issue is whether there will be a therapeutic gain with carbon ions or whether they will produce unwanted late effects on normal tissue. Brachytherapy and intra-operative radiation therapy have generally been used to treat microscopic residual disease in patients with sarcomas and offer advantages in selected clinical situations. Conclusions: These technologies permit delivery of dose to tumor cells with irradiation of more limited volumes of normal tissue. This improves local tumor control and reduces both acute and late morbidity. 60 RECENT DEVELOPMENTS OF LIGHT I O N THERAPY A. Brahme Medical Radiation Physics, Dept of Ontology-pathology, Karolinska Institutet, Box 260, SE-171 76 Stockholm, Sweden Radiation therapy is today in a state of very rapid development with new intensity modulated treatment techniques continuously being developed. This has made intensitymodulated electron and photon beams at least as powerful as today's uniform beam proton therapy. To be able to cure also the most advanced hypoxic and radiation resistant tumours of complex local spread, intensity modulated light ion beams will really be our ultimate tool for improved cancer cure and it will be only slightly more expensive than proton therapy, at least when based on a superconducting cyclotron and an excentric gantry design supplying beams to four surrounding treatment rooms. Since the radiation quality of light ions is significantly different from that of electrons, photons and protons it is even more important to develop radiobiologically optimised 3dimensional in vivo predictive assay based therapeutic pencil beam scanning techniques with light ions. Biologically optimized intensity modulated photons, electrons and light ions represent the ultimate development of radiation therapy where the absorbed dose and biological effect to normal tissues are as low as physically possible at the same time as the therapeutic effect on radiation resistant tumors is as high as possible. Moreover, with light ions the border region between the clinical target volume and surrounding normal tissues is as narrow as physically possible, the required number of treatment fractions is substantially reduced and the curative gain factor for hypoxic tumors approximately doubled compared to that for photons, electrons and protons. Taking all this information into account, the cost effectiveness of light ions becomes similar to that of modern intensity modulated radiation therapy, and about 2 to 3 times higher than that for proton therapy. The major reason for the improved cost effectiveness of the ions are the low number of treatment fractions possible in average in Chiba as few as 10 fractions are used due to their advantageous tumor to normal tissue RBE ratio whereas 25 to 30 fractions are needed with protons, photons and electrons. The only problem with the ions is the large capital cost requiring an initial investment in the order 100 MEUR. The major clinical advantages of light ion therapy are an increased therapeutic outcome in terms of improved local tumor control and quality of life, and an increased patient survival with a reduced risk for adverse normal tissue reactions. Light ions will be the ultimate radiation modality to exploit the genomic instability, the hallmark and
Mar ch 12 - 15
sometimes done automatically as a part of treatment plan optimization, may easily invalidate the principle of similarity. 58 SPOT SCANNING PROTON THERAPY: PLANNING A N D TREATMENT V E R I F I C A T I O N
TREATMENT
A.J. Lomax, F. Albertini, T. Boehringer, A. Bols, M. Bosshardt, A. Coray, G. Goitein, S. Lin, E. Pedroni, M. Stenecker, J. Verwey Department of Radiation Medicine, Paul Scherrer Institute, Switzerland Objective: Proton therapy provides many challenges to the treatment planning and verification of such treatments in the clinical routines. Here we describe some of the issues in these areas that we have addressed. Material and Methods: In the past 9 years we have learnt a number of things about the planning process. In particular, we have looked into the effects of different number of fields on the quality of proton plans for head and neck cases, studied the possibilities of reducing the number of applied Bragg peaks per field and also the possible detrimental effects of density heterogeneities and how to possibly avoid them. In terms of verification, we have introduced a field specific verification regime which was applied to all fields in the first 6 years, and is now applied only to more complex cases. An interesting area to be investigated however is the verification of the range of the protons in the patient, an area where proton radiography could be of great use. Results: For certain indications, there appears to be little advantage to increasing the number of fields beyond three, and have found that there is considerable scope for reducing the number of Bragg peaks delivered per field. A heterogeneity index has also been introduced into the planning system for predicting poor angles of approach to the tumour, and this has been found to be of some use for improving the homogeneity of dose to the tumour volume. Our field specific verification regime has shown that our delivery system can reliably and accurately deliver complex fields, but there is considerable work to be done in developing methods for the direct veification of range in the patient and for extending the verifications to multi-dimensional measurements. Conclusion: 9 years of experience has shown that dynami proton therapy can be delivered accurately and safely. However, there is much interesting work in the planning and verification of such treatments still to be done.
59 ADVANCED-TECHNOLOGY R A D I A T I O N THERAPY I N THE MANAGEMENT OF BONE AND SOFT TISSUE SARCOMAS
T.F. Delaney Massachusetts General Hospiatl, Boston, USA Objective: For patients with sarcoma, radiotherapy can be used as neoadjuvant, adjuvant, or primary therapy, depending upon the site and type of sarcoma, the surgical approach, and the efficacy of chemotherapy. Material and methods: Review of the current status of advanced technology radiation therapy in the management of bone and soft tissue sarcomas. Results: Advances in radiation therapy technology permit improved treatment for patients with bone and soft ~issue sarcomas. Most promising are intensity modulated radiation therapy (IMRT), proton beam or other charged particle radiation therapy, brachytherapy, and intra-operative radiation therapy. These deliver highly conformal radiation doses to complex target volumes near critical normal tissues. When combined with refinements in tumor target definition with MRI scan and PET/CT imaging, more precise delivery of radiation to the tumor while sparing adjacent normal tissues is possible. Intensity-modulated radiation therapy (IMRT) uses modifications in the intensity of the photon beam from a linear accelerator across the irradiated fields to enhance dose conformation in 3-dimensions. For proton beam radiation therapy, the nuclei of hydrogen atoms are accelerated in cyclotrons or synchrotrons, extracted and transported to treatment rooms where the proton beam undergoes a series of modifications (spreading, modulation and shaping) that conform the dose in a particular patient to the tumor target. Recent technical developments in hospital-based proton facilities with rotational gantries have generated considerable enthusiasm for the use of proton beams in radiation therapy.
$21
Comparable dose distributions to the tumor target itself can be achieved with intensity modulated photons or conformal proton beams. Because of their charge and mass, however, protons have a finite range and no dose is delivered distal to the desired target. In addition, dose proximal to the target is lower with protons and, up to certain depths in tissue, the penumbra of the beam is sharper. Proton beam therapy thus provides a means to reduce the volume of irradiated normal tissue and as well as the dose received by normal tissue. This may permit higher doses to the tumor and achieve a higher tumor control probability without increasing the frequency or severity of radiation-related morbidity. Additionally, the more conformal treatment volumes of proton therapy will result in reduced frequency and severity of co-morbidity between radiation and chemotherapy, thus improving tolerance of the patient to therapy and avoiding toxicity-induced interruptions in treatment that might compromise its efficacy. Interest in heavier charged particles has focused primarily on carbon ions. Still considered experimental, carbon ions have a greater relative biologic effect than protons; the pivotal issue is whether there will be a therapeutic gain with carbon ions or whether they will produce unwanted late effects on normal tissue. Brachytherapy and intra-operative radiation therapy have generally been used to treat microscopic residual disease in patients with sarcomas and offer advantages in selected clinical situations. Conclusions: These technologies permit delivery of dose to tumor cells with irradiation of more limited volumes of normal tissue. This improves local tumor control and reduces both acute and late morbidity. 60 RECENT DEVELOPMENTS OF LIGHT I O N THERAPY A. Brahme Medical Radiation Physics, Dept of Ontology-pathology, Karolinska Institutet, Box 260, SE-171 76 Stockholm, Sweden Radiation therapy is today in a state of very rapid development with new intensity modulated treatment techniques continuously being developed. This has made intensitymodulated electron and photon beams at least as powerful as today's uniform beam proton therapy. To be able to cure also the most advanced hypoxic and radiation resistant tumours of complex local spread, intensity modulated light ion beams will really be our ultimate tool for improved cancer cure and it will be only slightly more expensive than proton therapy, at least when based on a superconducting cyclotron and an excentric gantry design supplying beams to four surrounding treatment rooms. Since the radiation quality of light ions is significantly different from that of electrons, photons and protons it is even more important to develop radiobiologically optimised 3dimensional in vivo predictive assay based therapeutic pencil beam scanning techniques with light ions. Biologically optimized intensity modulated photons, electrons and light ions represent the ultimate development of radiation therapy where the absorbed dose and biological effect to normal tissues are as low as physically possible at the same time as the therapeutic effect on radiation resistant tumors is as high as possible. Moreover, with light ions the border region between the clinical target volume and surrounding normal tissues is as narrow as physically possible, the required number of treatment fractions is substantially reduced and the curative gain factor for hypoxic tumors approximately doubled compared to that for photons, electrons and protons. Taking all this information into account, the cost effectiveness of light ions becomes similar to that of modern intensity modulated radiation therapy, and about 2 to 3 times higher than that for proton therapy. The major reason for the improved cost effectiveness of the ions are the low number of treatment fractions possible in average in Chiba as few as 10 fractions are used due to their advantageous tumor to normal tissue RBE ratio whereas 25 to 30 fractions are needed with protons, photons and electrons. The only problem with the ions is the large capital cost requiring an initial investment in the order 100 MEUR. The major clinical advantages of light ion therapy are an increased therapeutic outcome in terms of improved local tumor control and quality of life, and an increased patient survival with a reduced risk for adverse normal tissue reactions. Light ions will be the ultimate radiation modality to exploit the genomic instability, the hallmark and