2020 Joint AAPM | COMP Virtual Meeting
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Session Title: FLASH Therapy – Current Status and the Way to the Clinic
Question 1: The normal tissue protection of FLASH-RT has been observed experimentally at mean dose rates as low as:
Reference:Favaudon, V., Caplier, L., Monceau, V., Pouzoulet, F., Sayarath, M., Fouillade, C., et al. (2014). Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice. Science Translational Medicine, 6(245), 245ra93–245ra93. http://doi.org/10.1126/scitranslmed.3008973
Choice A:0.4 Gy/s
Choice B:4 Gy/s
Choice C:40 Gy/s
Choice D:400 Gy/s
Choice E:4000 Gy/s
Question 2: The current explanation for the normal tissue protection of FLASH-RT is oxygen depletion and a reduction of indirect free radical damage.
Reference:Spitz, D. R., Buettner, G. R., Petronek, M. S., St-Aubin, J. J., Flynn, R. T., Waldron, T. J., & Limoli, C. L. (2019). An integrated physico-chemical approach for explaining the differential impact of FLASH versus conventional dose rate irradiation on cancer and normal tissue responses. Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology, 139, 23–27. http://doi.org/10.1016/j.radonc.2019.03.028
Choice A:True
Choice B:False
Question 3: It is hypothesized that ultra-high dose rates increase the simultaneous presence of many radicals during radiation, which leads to increased cell kill.
Reference:B. U. Zackrisson, U. H. Nyström & P. Ostbergh (1991) Biological Response In Vitro to Pulsed High Dose Rate Electrons from a Clinical Accelerator, Acta Oncologica, 30:6, 747-751
Choice A:True
Choice B:False
Question 4: What is the rate of oxygen depletion in water during irradiation?
Reference:Oxygen depletion in irradiated aqueous solutions containing electron affinic hypoxic cell radiosensitizers Michaels, Howard B. International Journal of Radiation Oncology, Biology, Physics, Volume 12, Issue 7, 1055 - 1058
Choice A:0.04 µM/Gy
Choice B:0.4 µM/Gy
Choice C:4 µM/Gy
Choice D:40 µM/Gy
Choice E:400 µM/Gy
Question 5: Protons and heavy ions do not produce the Flash effect because their high ionizing density produces molecular oxygen.
Reference:Colangelo, N. W., & Azzam, E. I. (2020). The Importance and Clinical Implications of FLASH Ultra-High Dose-Rate Studies for Proton and Heavy Ion Radiotherapy. Radiation Research, 193(1), 1–4. http://doi.org/10.1667/RR15537.1
Choice A:True
Choice B:False
Question 6: The ion collection efficiency of ionization chambers used in proton radiation at FLASH dose rates should be verified with a measurement that is independent of dose rate.
Reference:Diffenderfer ES, Kim MM, Verginadis II, Shoniyozov K, Hagan S, Avery S, et al. Implementation, Commissioning and In Vivo Validation of a Novel Proton Flash Radiotherapy System. Int. J. Radiat. Oncol. Biol. Phys. 2020;106(2):440–8.
Choice A:True
Choice B:False
Question 7: For cyclotron accelerated proton beams the ability to achieve FLASH dose rates does NOT depend on:
Reference:Diffenderfer ES, Kim MM, Verginadis II, Shoniyozov K, Hagan S, Avery S, et al. Implementation, Commissioning and In Vivo Validation of a Novel Proton Flash Radiotherapy System. Int. J. Radiat. Oncol. Biol. Phys. 2020;106(2):440–8.
Choice A:Beam energy or range in water
Choice B:Field size
Choice C:Cyclotron beam extraction efficiency
Choice D:Total dose
Choice E:Nozzle design
Question 8: A single dose of 41 Gy delivered with FLASH-RT to treat T2/T3 N0 M0 squamous cell carcinoma of the nasal planum in cats was found to induce:
Reference:Vozenin M-C, De Fornel P, Petersson K, Favaudon V, Jaccard M, Germond J-F, et al. The advantage of FLASH radiotherapy confirmed in mini-pig and cat-cancer patients. Clin Cancer Res. 2018.
Choice A:A complete macroscopic tumor response up to 16 months post-RT
Choice B:A transient tumor response followed by clinical recurrence 6 months post-RT
Choice C:Acute and late toxicities on the normal skin including moist desquamation and skin fibrosis
Choice D:Loss of smell
Question 9: Preclinical studies that have successfully observed a FLASH effect suggest
Reference:Wilson JD, Hammond EM, Higgins GS, Petersson K. Ultra-High Dose Rate (FLASH) Radiotherapy : Silver Bullet or Fool’s. Front Oncol. 2020.
Choice A:A dose modifying-factor on the tumor of 20-40 % in favor of FLASH-RT relative to conventional dose-rate RT
Choice B:A dose modifying-factor on the normal tissue of more than 200 % in favor of FLASH-RT relative to conventional dose-rate RT
Choice C:That the FLASH effect is only observed with doses < 5 Gy
Choice D:That hypo-fractionated regimen with doses > 5 Gy might be optimal to observe the FLASH effect
Question 10: Other potential clinical benefits of ultra-fast dose delivery could be:
Reference:Bourhis J, Montay-Gruel P, Gonçalves Jorge P, Bailat C, Petit B, Ollivier J, et al. Clinical translation of FLASH radiotherapy: Why and how? Radiother Oncol. 2019
Choice A:Patients can see fluorescence induced by the intense beam and know when the beam is on
Choice B:The very short ‘‘beam-on time” makes the intra-fraction motion management irrelevant
Choice C:The possibility to use pre-existing clinical LINACs to treat patients with FLASH-RT
Choice D:All of the above
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