Radiation Oncology/CNS/Protons

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Proton Therapy in CNS

By Site

Treatment Planning

Harvard
- 2010 PMID 20472369 -- "In vivo proton beam range verification using spine MRI changes." (Gensheimer MF, Int J Radiat Oncol Biol Phys. 2010 Sep 1;78(1):268-75. Epub 2010 May 17.)
  - Retrospective. 10 patients. Quantitative spine T1 MRI changes used to determine distal dose edge
  - Outcome: Distal fall-off sometimes further than planned, mean overshoot 1.9 mm (0.8-3.1 mm)
  - Conclusion: In vivo proton range verficiation, systematic overshoot but within treatment planning uncertainity
- 1995 PMID 8746720 -- "Comparison of proton and x-ray conformal dose distributions for radiosurgery applications." (Serago CF, Med Phys. 1995 Dec;22(12):2111-6.)
  - Treatment planning. Proton therapy (small number of fields), multiple-arc photons, conformal photons. Several SRS case
  - Outcome: Proton dose distributions superior to photons, difference negligible for smallest target volumes and largest for large target volumes

PSI
- IMRT vs IMPT; 2004 PMID 15519805 -- "Dose conformation of intensity-modulated stereotactic photon beams, proton beams, and intensity-modulated proton beams for intracranial lesions." (Baumert BG, Int J Radiat Oncol Biol Phys. 2004 Nov 15;60(4):1314-24.)
  - Treatment planning. 6 patients, brain lesions (multifocal, ovoid, irregular). Photon IMRT using micromultileaf collimators (mMLC) vs spot-scanning PT vs IMPT
  - PTV Outcome: PTV dose conformation equally good. 90% and 80% isodose volume comparable. 50% isodose IMRT better 3/6 and IMPT better 3/6. 30% isodose IMPT better
  - OAR Outcome: Concavities equally spared with IMRT and IMPT
  - Conclusion: PTV and OAR coverage equivalent; advantage of protons in lower integral dose
- 2nd cancers; 2002 PMID 12377335 -- "Potential reduction of the incidence of radiation-induced second cancers by using proton beams in the treatment of pediatric tumors." (Miralbell R, Int J Radiat Oncol Biol Phys. 2002 Nov 1;54(3):824-9.)
  - Treatment planning. 2 children, parameningeal rhabdomyosarcoma and medulloblastoma. Conventional photon vs. IMRT vs PT vs IMPT. Secondary cancer incidence estimated
  - Outcome: RMS: protons reduced expected incidence by > 2x over photons; MB protons reduced expected incidence by 8-15x over photons
  - Conclusion: Potential for significant reduction in secondary cancers with proton therapy
- 3D-CRT vs PT; 2001 PMID 11286852 -- "A comparison of dose distributions of proton and photon beams in stereotactic conformal radiotherapy of brain lesions." (Baumert BG, Int J Radiat Oncol Biol Phys. 2001 Apr 1;49(5):1439-49.)
  - Treatment planning. 7 patients, brain lesions (concave, ellipsoid, superficial close to OAR, irregular complex), stereotactic frame. Photon 3D-RT micromultileaf collimators (mMLC) vs spot-scanning energy-modulated proton beam
  - Outcome: High degree of conformation with both mMLC and PT; comparable conformity for 5/7 plans, PT better for complex or concave lesions or near OAR
  - Conclusion: For complex shapes or proximity to OAR, PT potentially better
- Paraorbital; 2000 PMID 10863085 -- "Optimizing radiotherapy of orbital and paraorbital tumors: intensity-modulated X-ray beams vs. intensity-modulated proton beams." (Miralbell R, Int J Radiat Oncol Biol Phys. 2000 Jul 1;47(4):1111-9.)
  - Treatment planning. 4 orbital/paraorbital tumors. IMRT vs IMPT.
  - Outcome: PTV coverage comparable. DVHs for OAR better with IMPT, though predicted severe NTCP equally low
  - Conclusion: Both IMRT and IMPT optimally treated PTV and reduced severe late toxicity; IMPT better at low/mid dose regions
- IMRT vs PT; 1999 PMID 10435821 -- "A treatment planning inter-comparison of proton and intensity modulated photon radiotherapy." (Lomax AJ, Radiother Oncol. 1999 Jun;51(3):257-71.)
  - Treatment planning. 9 cases (brain, H&N, abdomen, pelvis). 3D-CRT vs IMRT vs PT
  - Outcome: PT reduced integral dose 3x, and mean OAR and mean irradiated volume compared to both photon plans. However, comparable dose distribution >70% of prescribed dose. IMRT plan better in 3 cases for OAR avoidance
  - Conclusion: Protons reduce medium and low dose volumes, but high dose conformation comparable
- Supratentorial; 1997 PMID 9231669 -- "Potential role of proton therapy in the treatment of pediatric medulloblastoma/primitive neuroectodermal tumors: reduction of the supratentorial target volume." (Miralbell R, Int J Radiat Oncol Biol Phys. 1997 Jun 1;38(3):477-84.)
  - Treatment planning. 3 year old child with medulloblastoma. Photon whole brain (conventional 2 field) vs. hand-optimized photon brain (6 fields) vs. IMRT (9 fields) vs. proton (3 fields). Whole brain 30 Gy + posterior fossa/ventricle boost 10 Gy.
  - Outcome: both optimized photon plans only slightly worse than proton plan
  - Conclusion: Decrease in morbidity can be expected from protons and optimized photon plans compared to whole brain irradiation
- Craniospinal; 1997 PMID 9240650 -- "Potential role of proton therapy in the treatment of pediatric medulloblastoma/primitive neuro-ectodermal tumors: spinal theca irradiation." (Miralbell R, Int J Radiat Oncol Biol Phys. 1997 Jul 1;38(4):805-11.)
  - Treatment planning. 2 year old child with neuroblastoma, undergoing CSI. Single posterior 6 MV photon field vs. single posterior 100 MeV proton field, 30 Gy
  - Outcome: Target (spinal dural sac) coverage comparable. Vertebral body V50% photons 100% vs. protons 20%. Heart dose V60% photons 60% vs. protons 0%
  - Conclusion: Potential role for proton therapy in decreasing OAR dose during CSI irradiation

Southern Switzerland; 2003 PMID 12885446 -- "Radiotherapy of small intracranial tumours with different advanced techniques using photon and proton beams: a treatment planning study." (Bolsi A, Radiother Oncol. 2003 Jul;68(1):1-14.)
- Treatment planning. 12 patients (acoustic neuroma, meningioma, pituitary adenoma). 3D-CRT vs IMRT vs spot scanned PT (SSp) vs passive scatter PT (PSp)
- Outcome: Proton techniques superior to photon approaches for target uniformity/conformity and OAR sparing.
- Conclusion: Considering long life expectancy, long term toxicity and secondary tumors favor proton irradiation over photons