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La prescrizione della dose nei trattamenti stereo-RT e radiochirurgici: dall’ICRU a ROSEL ed altro
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La prescrizione della dose nei trattamenti stereo-RT e radiochirurgici: dall’ICRU a ROSEL ed altro

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24° CORSO RESIDENZIALE DI AGGIORNAMENTO ...

24° CORSO RESIDENZIALE DI AGGIORNAMENTO
con il patrocinio dell’Associazione Italiana di Radioterapia Oncologica (AIRO)
Moderna Radioterapia, Nuove Tecnologie e Ipofrazionamento della Dose

17 marzo 2014: La prescrizione della dose nei trattamenti stereo-RT e radiochirurgici: dall’ICRU a ROSEL ed altro

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  • 1. La prescrizione della doseLa prescrizione della dose nei trattamentinei trattamenti stereo-RT e radiochirurgici:stereo-RT e radiochirurgici: dall’ICRU a ROSEL ed altrodall’ICRU a ROSEL ed altro Giovedì 21 Novembre 2013 – Deodato, Cilla, De Filippo, Masiello
  • 2. When delivering a radiotherapy treatment, parameters such as volume and dose have to be specified for different purposes: prescription, recording, and reporting. It is important that clear, well defined and unambigous concepts and parameters are used for reporting purposes to ensure a common language between different centers. When delivering a radiotherapy treatment, parameters such as volume and dose have to be specified for different purposes: prescription, recording, and reporting. It is important that clear, well defined and unambigous concepts and parameters are used for reporting purposes to ensure a common language between different centers.
  • 3. ICRU International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 The International Commission on Radiation Units and Measurements (ICRU), since its inception in 1925, has had as its principal objective the development of internationally acceptable recommendations regarding: • Quantities and units of radiation and radioactivity • Procedures suitable for the measurement and application of these quantities in clinical radiobiology • Physical data needed in the application of these procedures, the use of which tends to assure uniformity in reporting
  • 4. Target volumes – ICRU 50 e 62 International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 ICRU 50 (1993): 1993 to 1999 ICRU 62 (1999): 1999 to till date
  • 5. ICRU Reports – ICRU 50 International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 Volumes defined prior to treatment planning : - Gross Tumor Volume (GTV) - Clinical Target Volume (CTV) Volumes defined during the treatment planning : - Planning target Volume (PTV) - Organs at risk - Treated Volume - Irradiated Volume
  • 6. GROSS TUMOR VOLUME ( GTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 • Gross palpable or visible/demonstrable extent and location of the malignant growth • It consists of : - Primary tumor - Metastatic lymphadenopathy - Other metastasis • Corresponds to those parts of the malignant growth where the tumor density is largest. • If the tumor has been removed prior to radiotherapy then no GTV can be defined.
  • 7. GROSS TUMOR VOLUME ( GTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 8. CLINICAL TARGET VOLUME ( CTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 • It is a tissue volume that contains a GTV and/or subclinical microscopic disease, which has to be eliminated • This volume has to be treated adequately in order to achieve the aim of therapy : cure or palliation • The delineation of this volume requires consideration of factors like local invasive capacity of the tumor and its potential to spread to different regions ( eg: regional lymph nodes).
  • 9. CLINICAL TARGET VOLUME ( CTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 10. PLANNING TARGET VOLUME ( PTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 • It is a geometrical concept, and is defined to select appropriate beam sizes and arrangements, taking into consideration the net effect of all possible geometrical variations, in order to ensure that the prescribed dose is actually absorbed in the CTV. • It is used for dose planning and for specification of dose. • It has to be clearly indicated on sections used for dose planning and the dose distribution to the PTV has to be considered to be representative of the dose to the CTV.
  • 11. PLANNING TARGET VOLUME ( PTV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 12. TREATED VOLUME - 1 • It is a volume enclosed by an isodose surface, selected and specified by the radiation oncologist as being appropriate to achieve the purpose of treatment ( tumor eradication or palliation ). • It may closely match to the PTV or may be larger than the PTV. • If, however, it is smaller than the PTV, or not wholly enclosing the PTV, then the probability of tumor control is reduced and the treatment plan has to be revaluated or the aim of the therapy has to be reconsidered. International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 13. TREATED VOLUME - 2 Reasons for identification of Treated Volume are : 1.The shape and size of the Treated Volume relative to the PTV is an important optimization parameter. 2.Also, a recurrence within a Treated Volume but outside the PTV may be considered to be a “true”, “in-field” recurrence due to inadequate dose and not a “marginal” recurrence due to inadequate volume. International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 14. ORGANS AT RISK ( OR ) • These are normal tissues whose radiation sensitivity may significantly influence the treatment planning and/or prescribed dose. • They may be divided into 3 classes : 1. Class I : Radiation lesions are fatal or result in severe morbidity. 2. Class II : Radiation lesions result in mild to moderate morbidity. 3. Class III : Radiation lesions are mild, transient, and reversible, or result in no significant morbidity. International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 15. IRRADIATED VOLUME ( IRV ) • It is that tissue volume which receives a dose that is considered significant in relation to normal tissue tolerance. • It depends on the treatment technique used. International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993
  • 16. ICRU 50 - Summary International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy, ICRU REPORT 50, 1993 Irradiated Volume Treated Volume Planning Target Volume (PTV) Clinical Target Volume (CTV) Gross Tumor Volume (GTV)
  • 17. ICRU REPORT 62 ( Supplement to ICRU REPORT 50 ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • Gives more detailed recommendations on the different margins that must be considered to account for anatomical and geometrical variations and uncertainties • Introduces a Conformity Index (CI) • Gives information about how to classify Organs at Risk • Introduces a Planning Organ at Risk Volume (PRV) • Gives recommendations on graphics
  • 18. ICRU REPORT 62 International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 Volumes defined prior to treatment planning : - Gross Tumor Volume (GTV) - Clinical Target Volume (CTV) Volumes defined during the treatment planning : - Planning target Volume (PTV) - Treated Volume → must be enclosed in the 95% isodose - Irradiated Volume → must be enclosed in the 50% isodose - Planning Organ at Risk Volume (PRV) Same as ICRU 50
  • 19. INTERNAL MARGIN (IM) AND INTERNAL TARGET VOLUME (ITV) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It is the margin given around the CTV to compensate for all variations in the site, size and shapes of organs and tissues contained in/or adjacent to CTV • These may result from respiration, different fillings of the bladder and rectum, swallowing, heart beat, movements of bowel etc. • These are physiological variations which are very difficult to control and result in changes in the site, size and shape of CTV.
  • 20. SET-UP MARGIN (SM) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • There can be many uncertainties (inaccuracies and lack of reproducibility) in patient positioning and alignment of the therapeutic beams during treatment, planning and through all treatment sessions. • These uncertainties depend on factors like : • variations in pt. positioning • mechanical uncertainties of the equipment (sagging of gantry, collimators, and couch) • dosimetric uncertainties • transfer set-up errors from CT & simulator to the treatment unit • human factors SET-UP MARGIN (SM) is the margin that must be added to account specifically for uncertainties (inaccuracies and lack of reproducibility) in patient positioning and aligment of the therapeutic beams during treatment planning and through all treatment sessions.
  • 21. CONFORMITY INDEX (CI) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It is defined as the quotient of the Treated Volume and the volume of PTV. • It can be employed when the PTV is fully enclosed by the Treated Volume. • It can be used as a part of the optimization procedure. CI = TV/PTV
  • 22. ORGANS AT RISK International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • According to the functional models based on the FSU (Functional Sub Unit) concept [ Withers et al., Kallman et al., and Olsen et al. ] for the purpose of evaluation of the volume-fractionation-response, the tissues of an Organ at Risk are considered to be functionally either “serial” “parallel” or “serial-parallel” structures. Spinal cord Lung Heart
  • 23. PLANNING ORGAN AT RISK VOLUME ( PRV ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • This is a volume which gives into consideration the movement of the Organs at Risk during the treatment • An integrated margin must be added to the Organ at Risk to compensate for the variations and uncertainties, using the same principle as PTV and is known as the Planning Organ at Risk volume ( PRV ) • A PTV and PRV may occasionally overlap
  • 24. ICRU 62 International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 GTVCTVITVPTVORPRV TVIrradiated volume
  • 25. ADSORBED DOSE DISTRIBUTION International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 •The dose given to the tumor should be as homogenous as possible. • In cases of heterogeneity of doses, the outcome of the treatment cannot be related to the dose. Also, the comparison between different patient series becomes difficult. • However, even if a perfectly homogenous dose distribution is desirable, some heterogeneity is accepted due to technical reasons. •The heterogeneity should be foreseen while prescribing a treatment, and, in the best technical and clinical conditions should be kept within +7% and -5% of prescribed dose (Wittkamper et al., Brahme et al., Mijnheer et al.)
  • 26. MAXIMUM DOSE ( Dmax ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It is the maximum dose to the PTV and the Organ at Risk • The maximum dose to normal tissue is important for limiting and for evaluating the side-effects of treatment • Dose is reported as maximum only when a volume of tissue of diameter more than 15mm is involved (smaller volumes are considered for smaller organs like eye, optic nerve, larynx) • When the maximum dose outside PTV exceeds the prescribed dose, then a “Hot Spot” can be identified
  • 27. HOT SPOTS International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It represents a volume outside the PTV which receives a dose larger than 100% of the specified dose • A Hot Spot is considered significant only if the minimum diameter exceeds 15mm (in smaller organs like eye, optical nerve, larynx etc. a diameter smaller than 15mm is also considered significant).
  • 28. MINIMUM DOSE ( Dmin ) International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It is the smallest dose in a defined volume. • In contrast to maximum adsorbed dose, no volume limit is recommended when reporting minimum dose.
  • 29. ICRU REFERENCE POINT International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 It has to be selected according to the following general criteria : - the dose at the point should be clinically relevant - the point should be easy to define in a clear and unambiguous way - the point should be selected so that the dose should be accurately determined - the point should be in a region where there is no steep dose gradient
  • 30. ICRU REFERENCE POINT -2 International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 The recommendations will be fulfilled if the ICRU reference point is located : • always at the centre ( or in the central part ) of PTV, and • when possible, at the intersection of the beam axes.
  • 31. ICRU REFERENCE DOSE International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 It is the dose at the ICRU Reference Point and should always be reported. • Since the CTV can move in space and can change size and shape, the dose at the center, the maximum and the minimum dose, and the dose- volume histograms cannot be determined with high accurancy • As far as the dose at the center of the CTV is concerned, its value is generally close to that of the dose at the center of the PTV, which thus can be reported as a reasonable estimate of the dose at the center of the CTV
  • 32. REPORTING International commision on Radiation Units, Prescribing, Recording and Reporting Photon Beam Therapy (Supplement tp ICRU Report 50), ICRU REPORT 62, Issued 1 November 1999 • It should be done in order to make exchange of information between different centers. • It is important that the treatments performed in various centers be reported in the same way, using the same concepts and definitions. • According to the recommendations of ICRU, as a basic requirement, the following doses should always be reported :  the dose at ICRU reference point  the maximum dose to the PTV  the minimum dose to the PTV
  • 33. Physics of Radiosurgery • Stereotactic radiosurgery (SRS) involves the use of numerous beamlets of radiation aimed precisely at an immobilized target to deliver a single session of high dose radiation • The term “stereotactic” implies the targeting, planning, and directing of therapy using beams of radiation along any trajectory in 3-D space toward a target of known 3-D coordinates • The main dose is deposited at the intersection of these beamlets with a steep dose fall-off outside the target • Radiosurgery becomes prohibitive at size in excess of 4 to 5 cm • The mainly used sources are:  Cobalt-60 (Gamma-Knife and the Rotating Gamma System)  X-Rays (Linear Accelerator)  Protons
  • 34. Radiobiology • The use of single fraction to treat a small volume differs significantly from conventional EBRT • There is a increased biologic effect on normal tissues more pronounced than it is on tumors FRT SBRT EXPLOIT TEMPORAL EFFECTS OF CELL CYCLE DISTRIBUTION NO TAKE ADVANTAGE OF THE REOXYGENATION OF THE TUMOR NO REPOPULATION MINIMIZES THE EFFECT OF REPOPULATION LESS ENDOTHELIAL APOPTOSIS ENDOTHELIAL APOPTOSIS
  • 35. Historical Landmarks in Radiosurgery - 1 YEAR AUTHOR LOCATION EVENT 1951 Leksell Stokcholm Invention of “Stereotactic Radiosurgery” using rotating orthovoltage unit 1952 Lawrence Berkeley Use of heavy particle treatment for pituitary for cancer pain 1964 Kiellberg Boston Use of protobeam for inntracranial radiosurgery 1967 Leksell Stockholm Invention of Gammaknife using cobalt-60 sources 1970 Steiner Stockholm Use of Gammaknife for AVM’s 1980 Fabrikant Berkley Use of Helium ions for AVM’s
  • 36. The Past of Radiosurgery Orthovoltage Xrays tube Particle beam Lars Leksell - 1951 • Coined the term “radiosurgery” • First procedures done with orthovoltage Xrays tube • After initially experimenting with particle beam, designed Gammaknife with 179 cobalt-60 sources in a Hemisphere array Acta Chirur Scand, The stereotaxic method and radiosurgery of the brain. 1951 Dec13;102(4):316-9
  • 37. Historical Landmarks in Radiosurgery - 2 YEAR AUTHOR LOCATION EVENT 1982 Betti, Colombo Buenos Aires Vicenza Independent development of a system adapting LINAC’s for radiosurgery 1986 Lutz/Winston JCRT Development of LINAC based SRS based on common stereotactic frame 1987 Lundsford Pittsburgh First Gammaknife installed in the US 1991 Friedman/Bova Florida Development of a more reliable technique for highly conformal radiosurgery 1991 Lax Blomgren Karolinska First to propose extending SRS outside of the skull 1992 Loeffler/Alexander Boston First commercially Built dedicated SRS LINAC (Varian-SRS) 1993 Laing Boston Gill-Thomas-Cosman relocatable frame
  • 38. Dose and prescription in SRS with linear accelerator • The average “treatment” distance error for a target was found to be 1.33+/- 0.64 mm where 0.64 mm is the standard deviation for a single treatment • Prescribing dose to the 80% surface (target center being 100%) Lutz W, Winston KR e al A system for stereotactic radiosurgery with a linear accelerator, Int J Radiation Oncol Biol Phys Vol 14 pp 373-381
  • 39. ASTRO /ACR guidelines for the performance of SRS Seung SK, Larson DA e al. American College of Radiology (ACR) and American Society for Radiation Oncology (ASTRO) Practice Guideline for the
  • 40. SBRT Dose prescription (lung) Nagata Y, Matsuo Y, Takayama K, NorihisaY, Mizowaaki T, MitsumoriM, Shibuya K, Yano S, Narita Y, Hiraoka M. Current status of stereotactic body radiotherapy for lung cancer. Int J Clin Oncol 2007
  • 41. SBRT Dose prescription (lung) Wulf J, Bajer K, Mueller G, Flentje MP. Dose-response in stereotactic irradiation of lung tumors. Radiotherapy and Oncology 2005
  • 42. SBRT Dose prescription (lung) Wulf J, Bajer K, Mueller G, Flentje MP. Dose-response in stereotactic irradiation of lung tumors. Radiotherapy and Oncology 2005
  • 43. SBRT Dose prescription (liver) Wulf J, Guckemberg M, Haedinger U, Oppitz U. Mueller G, Baier K & Flentje M. Stereotactic radiotherapy of primary liver cancer and hepatic metastases. Acta Oncologica 2006
  • 44. SBRT Dose prescription (brain) Ohtakara K, Hayashi S, Tanaka Hoshi H. Consideration of optimal isodose surface selection for target coverage in micro-multileaf collimator- based stereotactic radiotherapy for large cystic brain metastases: comparison of 90, 80 and 70% isodose surface-based planning. The Brithish Journal of Radiology 2012
  • 45. • Users have a wide choice of prescription modalities • Resulting dose distribution is influenced by treatment delivery platform, target geometry, treatment site, ….. • The nature of dose falloff into normal tissue (gradient dose) remain less optimized • This gradient is influenced by: number of beams, beam shape, beam direction and ….. beam aperture dimension (block margin) choice of target prescription isodose Introduction to ROSEL study
  • 46. Hurkmans e al, Recommendations for implementing stereotactic radiotherapy in peripheral stage IA non-small cell lung cancer: report from the Quality Assurance Working Party of the randomised phase III ROSEL study, Radiation Oncology, January 2009, 4:1 BLOCK MARGIN: the fundamental picture (1)
  • 47. Hong e al: LINAC-based SRS: Inhomogeneity, conformity and dose fall off, Med Phys., Vol 38, No. 3, March 2011 BLOCK MARGIN: the fundamental picture (2)
  • 48. Hurkmans e al, Recommendations for implementing stereotactic radiotherapy in peripheral stage IA non-small cell lung cancer: report from the Quality Assurance Working Party of the randomised phase III ROSEL study, Radiation Oncology, January 2009, 4:1 Herfarth KK, Stereotactic irradiation of liver metastases, Radiologe 2001 Jan; 41(1): 64-8
  • 49. A simulated dose prescription on liver: UCSC Roma/Campobasso
  • 50. LIVER 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Volume Dose Margin 5 mm Margin 2.5 mm Margin 0 mm PTV 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Volume Dose Margin 5 mm Margin 2.5 mm Margin 0 mm GTV 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Volume Dose Margin 5 mm Margin 2.5 mm Margin 0 mm V7Gy<50% V12Gy<30% A simulated dose prescription on liver: UCSC Roma/Campobasso
  • 51. Negative Margin