Secondary Neutrons in Proton and Ion Therapy

Secondary Neutrons in Proton and Ion Therapy L. Stolarczyk Institute of Nuclear Physics PAN, Poland on behalf of WG9 EURADOS

Acknowledgments EURADOS Workig Group 9 Roger Harrison Jean Marc Bordy Carles Domingo Francesco d Errico Jad Farah Angela Di Fulvio Željka Knežević Saveta Miljanić Pawel Olko

Controversy around secondary radiation doses in radiotherapy Source: Eric J. Hall, Intensity-modulated radiation therapy, protons, and the risk of second cancers, Int. J. Rad. Onc. Biol. Phys. 65 (2006) 1-7.

Controversy around secondary radiation doses in radiotherapy Does it make any sense to spend over $100 million on a proton facility, with the aim to reduce doses to normal tissues, and then to bathe the patient with a total body dose of neutrons ( )? Hall, Technol. in Ca. Res. Treat., 2007,6,31-34 Source: Eric J. Hall, Intensity-modulated radiation therapy, protons, and the risk of second cancers, Int. J. Rad. Onc. Biol. Phys. 65 (2006) 1-7.

Research projects and groups working on secondary radiation Allegro Group Andante Group Eurados WG9 IRSN PSI University of Texas MD Anderson Cancer Center Massachusetts General Hospital University of Wollongong Many more

Aim of presentation Dosimetry data Epidemiological risk assessment Probability of secondary cancer

Plan Principles of conventional and hadron therapy Secondary radiation in radiotherapy Secondary radiation in conventional and conformal radiotherapy Neutrons in proton radiotherapy Passive beam delivery Active scanning Neutrons in carbon radiotherapy Comparison of dosimetric studies on secondary radiation Conclusion

Depth dose distribution in radiotherapy

Advantages of hadron radiotherapy Relatively low entrance dose (plateau) Maximum dose at depth (Bragg peak) Rapid distal dose fall-off Energy modulation (Spread-Out Bragg Peak) Relative biological effectiveness RBE of protons and carbon ions

Techniques of beam modulation - passive

Techniques of beam modulation - active Source: http://radmed.web.psi.ch/asm/gantry/scan/n_scan.html

Dose distribution Clinical point of view The treatment of posterior fossa Source: Greco C. Current Status of Radiotherapy With Proton and Light Ion Beams. American CANCER society April 1, 2007 / Volume 109 / Number 7 The dose to 90% of the cochlea was reduced from 101% with standard photons, to 33% with IMRT, and to 2% with protons

Secondary radiation in radiotherapy Generated in treatment nozzle and patient body X rays: scattered X rays, secondary gamma radiation, photoneutrons Hadron therapy: neutrons, charged particles, prompt gamma radiation, characteristic X rays, bremssthralung radiation and residual radiation from radioactivation Low dose region

Interactions of neutrons in tissue Thermal neutrons Neutron capture by nitrogen 14 N(n,p) 14 C, E tr = 0.62 MeV Neutron capture by hydrogen 1 H(n,γ) 2 H, E γ = 2.2 MeV Intermediate and fast neutrons Elastic scattering E tr 2M am E ( M M a n n ) 2

Courtesy of A. Di Fulvio Methods of neutron dosimetry in secondary radiation field Passive detectors Track detectors Bubble detectors Activation foils TLDs with 6 Li and 7 Li Semiconductor detectors Active detectors Rem counters TEPC Recombination chambers Bonner spheres Monte Carlo simutations Courtesy of T. Horwacik

Secondary doses in radiotherapy target Dose Equivalent Ambient dose equivalent Secondary dose Target dose µsv (µgy) secondary doses Gy

EURADOS WG9 experiments in conventional RT (scattered X-rays) Passive dosimeters for X rays measurements outside the target volume 30 x 30 x 60 cm Source: Stolarczyk, PhD thesis, 2012

EURADOS WG9 experiments in conventional RT (scattered X-rays) Comparison of out-of-field X rays doses for prostate treatment 0.6 1.1 msv/gy Source: Stolarczyk, PhD thesis, 2012

EURADOS WG9 experiments in conventional RT (neutrons) Peak around 0.6 MeV in the energy spectra outside the target Photoneutrons for photon energy as low as 6 MV Neutron dose in IMRT higher than in conformal radiotherapy Neutron spectrum measured with RDNS Source: Di Fulvio, A., Clinical simulations of prostate radiotherapy using BOMAB-like phantoms: Results for neutrons, Radiat. Measurements, 2013, available online

EURADOS WG9 experiments in conventional RT Peak around 0.6 MeV in the energy spectra outside the target Photoneutrons for photon energy as low as 6 MV Beryllium neutron separation energy 1.66 MeV Neutron dose in IMRT higher than in conformal radiotherapy Total neutron dose equivalent for prostate treatments VMAT IMRT TOMO Source: Di Fulvio, A., Clinical simulations of prostate radiotherapy using BOMAB-like phantoms: Results for neutrons, Radiat. Measurements, 2013, available online

EURADOS WG9 experiments in conventional RT Peak around 0.6 MeV in the energy spectra outside the target Dose equivalent profiles for prostate treatment measured by SDD and PADC Photoneutrons for photon energy as low as 6 MV Neutron dose in IMRT higher than in conformal radiotherapy 3 20 µsv/gy Source: Di Fulvio, A., Clinical simulations of prostate radiotherapy using BOMAB-like phantoms: Results for neutrons, Radiat. Measurements, 2013, available online

Plan Principles of conventional and hadron therapy Secondary radiation in conventional and conformal radiotherapy Neutrons in proton radiotherapy Passive beam delivery Active scanning Neutrons in carbon radiotherapy Comparison of dosimetric studies on secondary radiation Conclusion

Main sources of out-of-field doses in passive scattering proton RT conforms the dose distribution to the shape of the tumour shifts the range of the proton beam spreads out the Bragg peak across the depth of the target volume IFJ PAN proton facility

Dosimetric studies on neutron doses in passive scattering proton RT The decrease of neutron doses with distance from the field edge 0.3 msv/gy Source: Wroe, A., 2007 Out-of-field dose equivalents delivered by proton therapy of prostate cancer. Med. Phys. 34, 3449 56

Dosimetric studies on neutron doses in passive scattering proton RT The increase of neutron dose equivalent with the energy of primary proton beam Source: Mesoloras, G., et al., 2006. Neutron scattered dose equivalent to a fetus from proton radiotherapy of the mother. Med. Phys. 33, 2479 90

Dosimetric studies on neutron doses in passive scattering proton RT The increase of neutron dose with modulation for low energy proton beams Modulation depth m Source:L. Stolarczyk, PhD thesis, 2012

Dosimetric studies on neutron doses in passive scattering proton RT The increase of neutron dose equivalent with modulation for high energy proton beams Modulation depth m Source: Zheng, Y., 2007. Monte Carlo study of neutron dose equivalent during passive scattering proton therapy. Phys. Med. Biol. 52, 4481-4496

Dosimetric studies on neutron doses in passive scattering proton RT The decrease of neutron ambient dose equivalent with aperture size for small fields IFJ PAN Cyclotron Center Source:L. Stolarczyk, PhD thesis, 2012

Dosimetric studies on neutron doses in passive scattering proton RT The decrease of neutron dose equivalent with aperture size for large fields Source: http://www.nytimes.com/2007/12/26/business/26proton.html?_r=0 Source: Mesoloras, G., et al., 2006. Neutron scattered dose equivalent to a fetus from proton radiotherapy of the mother. Med. Phys. 33, 2479 90

Dosimetric studies on neutron doses in passive scattering proton RT Neutron dose equivalent variation with air gap Source: Paganetti H., et al., 2005. Proton Beam Radiotherapy- The State of the Art Source: Mesoloras, G., et al., 2006. Neutron scattered dose equivalent to a fetus from proton radiotherapy of the mother. Med. Phys. 33, 2479 90

Minimization of the undesired dose to the patient in passive scattering proton RT Beam collimation Shielding around treatment room Patient shielding inside therapy room Using an optimized pre-collimator/collimator Source:L. Stolarczyk, PhD thesis, 2012

Minimization of the undesired dose to the patient in passive scattering proton RT Beam collimation Shielding around treatment room Patient shielding inside therapy room Using an optimized pre-collimator/collimator hybrid plastic-metal collimator + patient-specific collimators Source: Brenner, D.,2009. Reduction of the secondary neutron dose in passively scattered proton radiotherapy, using an optimized precollimator/collimator, Phys. Med. Biol. 54, 6065 6078

Plan Principles of conventional and hadron therapy Secondary radiation in conventional and conformal radiotherapy Neutrons in proton radiotherapy Passive beam delivery mode Active scanning Neutrons in carbon radiotherapy Comparison of dosimetric studies on secondary radiation Conclusion

Dosimetric studies on neutron doses in scanning proton RT Smaller irradiated high-dose volume Ideally: no scattering devices in the treatment nozzle or patient apertures and compensators Reality: possibility of use of range shifter and patient collimator The majority of the secondary neutrons generated in the patient body

Dosimetric studies on neutron doses in scanning proton RT The decrease of neutron doses with distance from the field edge 0.015 msv/gy Source: Schneider U., 2002 Secondary neutron dose during proton therapy using spot scanning Int. J. Radiat. Oncol. Biol. Phys. 53244 51

Dosimetric studies on neutron doses in scanning proton RT Neutron doses equivalent at different lateral distences from the field edge Source: S. Dowdell, PhD thesis, 2011

Dosimetric studies on neutron doses in scanning proton RT Neutron doses equivalent at different lateral distences from the field edge 0.013 msv/gy Source: S. Dowdell, PhD thesis, 2011

Dosimetric studies on neutron doses in scanning proton RT Fluence of secondary thermal neutrons measured with TLDs Source: R. Kaderka, PhD thesis, 2011

Dosimetric studies on neutron doses in scanning proton RT TL signal for the TLD 600 in all irradiation techniques Source: R. Kaderka, PhD thesis, 2011

Dosimetric studies on neutron doses in carbon RT Sharper dose fall-off than protons close to the target The dose far out-of-field of carbon ions higher than for protons Increasing peripheral dose with increasing incident energy Increasing out-of-field dose with the field size (one order of magnitude for a 300 MeV/u carbon beam with field sizes of 5x5 and 10x10cm 2 ) Source: R. Kaderka, PhD thesis, 2011

Dosimetric studies on neutron doses in carbon RT TL signal for the TLD 600 in all irradiation techniques Source: R. Kaderka, PhD thesis, 2011

Dosimetric studies on neutron doses in carbon RT The decrease of neutron doses with distance from the field edge Source: Yonai, S., Matsufuji, N., Kanai, T., et. al., 2008. Measurement of neutron ambient dose equivalent in passive carbon-ion and proton radiotherapies. Med. Phys. 35, 4782-4792 0.6 0.95 msv/gy

Comparison of dosimetric studies on secondary radiation (prostate treatment) Treatment technique Dose equivalent per target dose [msv/gy] Passive proton RT 0.3 Wroe, 2008 Scanning proton RT 0.015 Schneider, 2002 Passive carbon RT 0.60 0.95 Yonai, 2008 Scanning carbon RT 0.06 0.08 Yonai, 2013 CRT 18 MV 1.7 Kry, 2005 IMRT (6 MV 18 MV) 0.6 8.1 Kry, 2005 Miljanic, 2012 Di Fulvio, 2012 TOMO 6MV 0.9 VMAT 6 MV 0.7 Miljanic, 2012 Di Fulvio, 2012 Miljanic, 2012 Di Fulvio, 2012 Source: http://www.nytimes.com/2007/12/26/business/26proton.html?_r=0

Comparison of dosimetric studies on secondary radiation (prostate treatment) Treatment technique Effective dose [msv] Passive proton RT 187 Newhauser, 2009 Passive proton RT (eye treatment) 0.2 Stolarczyk, 2011 Scanning proton RT 89 Newhauser, 2009 Scanning carbon RT 195 Schardt, 2006 CRT 18 MV 230 Kry, 2005 IMRT (6 MV 18 MV) 260 630 Kry, 2005 Source: http://www.nytimes.com/2007/12/26/business/26proton.html?_r=0

Conclusions Does it make any sense to spend over $100 million on a proton facility, with the aim to reduce doses to normal tissues, and then to bathe the patient with a total body dose of neutrons ( )? Hall, Technol. in Ca. Res. Treat., 2007,6,31-34 While we agree that proton therapy represents a major advance, we differ with Hall s other key statements and inferences Newhauser, Phys. Med. Biol., 2009,54,2277 2291

Thank you for your attention ;)