Particle therapy

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The particle therapy , or particle therapy ( English particle therapy ), more hadron therapy is a method of radiation therapy , in which as part of a cancer treatment of the tumor with high-energy positive ions (usually protons or carbon ions is irradiated). The particles are accelerated in a cyclotron or synchrotron . A synchrotron is necessary for carbon ions in order to achieve the necessary penetration depths (up to 30 cm).

properties

The advantage of particle therapy compared to conventional radiation therapy with photons is the completely different penetration behavior of the particles (particles). The interaction of the introduced particles with the tissue is strongly speed-dependent: the energy output per path length is roughly inversely proportional to the speed square. As the particles pass through the tissue, the deeper they penetrate, the slower they are. At high speed (particle energy> 50 MeV / u ) their effect is relatively small. Only towards the end of their range do they develop their strong effect. There the effect increases very strongly over a distance of a few millimeters and then drops to zero (for protons) or almost to zero (for carbon ions). The depth dose profile generated in this way is called the Bragg peak . The energy of the particle when it leaves the accelerator determines the penetration depth and the location of the maximum effect. This behavior makes it possible to deposit a very high radiation dose in the tumor and at the same time to spare other tissue located in front of the tumor - especially organs at risk . Because the particle beam can be quickly deflected transversely to the beam direction with electromagnets, the target volume can be processed in layers precisely according to the shape of the tumor using the magnetic raster scanning method (combined with the energy variation).

Investments

Despite the high equipment requirements (cyclotron or synchrotron), particle therapy is already being used routinely in thirteen countries around the world, and over 200,000 patients had been treated by the end of 2019, including over 25,000 patients with particles heavier than protons (mostly helium and carbon). The list of treatments performed worldwide to date is continuously updated by the Particle Therapy Co-Operative Group .

Systems in Germany

In Germany, particle therapy was initially only possible in facilities whose main purpose was physical research. In the years 1998–2008, over 1200 eye cancer patients were treated with protons at the ISL ion beam laboratory of the Hahn-Meitner-Institut in Berlin. Until October 2007 there was a small therapy facility at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, where carbon ions were used (450 patients in total). In 2009 a private proton therapy facility in Munich received its operating permit. The Heidelberg Ion Beam Therapy Center (HIT) also went into operation in November 2009 . A planned system by Siemens at the University Medical Center Schleswig-Holstein , Campus Kiel, will only be implemented as a conventional radiation therapy center. A pure proton therapy facility has been in operation in the West German Proton Therapy Center in Essen (WPE) since spring 2013 , which had treated more than 1,500 patients by December 2018. In October 2015, the Marburg Ion Beam Therapy Center (MIT) began operations at the University Clinic in Marburg . This facility, which is similar to the HIT, is sponsored by the University of Heidelberg and the Rhön-Klinikum AG, which also operates the University Clinic in Gießen and Marburg . In Germany there are two plants in Heidelberg and Marburg that use protons and carbon ions for therapy.

Proton therapy

Therapy with carbon ions

With carbon ions, there is a strong additional advantage: Due to the high local ionization density at the end of the range, correlated damage (mainly to the DNA structures) occurs more frequently in the target volume, which means that the DNA of the cancer cells is more difficult to repair by repair enzymes than in the healthy one in front of it Tissue (penetration channel). Compared to photons, this has an effect of the same dose in the target volume that is up to three times better.

The Particle Therapy Co-Operative Group provides continuously updated lists of active and planned hadron therapy centers. At the end of 2008 only two centers for carbon ions were in operation worldwide, both in Japan: HIMAC in Chiba and HIBMC in Hyogo . In Germany, the first hadron therapy center with the Heidelberg ion beam therapy center was opened on November 2, 2009 at the Heidelberg University Hospital . In 2015, the second, similarly built system followed at the Marburg University Hospital.

outlook

Protons and carbon ions are ideal for developing a local therapeutic technique aimed at healing effects, even for problematic cases (malignant tumors which, due to their proximity to sensitive organs, are neither accessible to surgery nor to conventional radiation therapy).

According to the current state of clinical research, there is an advantage for highly ionizing radiation (carbon ions) for the treatment of certain malignant tumors of the main salivary glands , of adenocarcinomas of the prostate, soft tissue sarcomas , local recurrences of the rectum and of adenoid cystic tumors of the nasal cavities. Radiation therapy with protons is well suited for tumors close to the surface, such as choroidal melanomas , chordomas and chondrosarcomas , and shows positive approaches for esophageal carcinomas, hepatocellular tumors, adenocarcinomas of the prostate, meningiomas and pituitary tumors.

Since the total dose deposited with radiation therapy with ion beams is lower than with conventional radiation with X-ray or gamma radiation or with neutron radiation, ion therapy is the more advantageous concept for almost all tumors that are radiation-treated, including tumors of the main salivary glands Nasal cavities, central nervous system, non-small cell lung cancer, and tumors in children. It is not yet possible to conclusively assess whether protons or carbon ions are the clinically more favorable particle beams. It is clear, however, that particle therapy with protons, but above all with carbon ions, is considerably better than neutron therapy.

literature

  • C. Greco, S. Wolden: Current status of radiotherapy with proton and light ion beams. In: Cancer. 109 (7), Apr 1, 2007, pp. 1227-1238. Review. PMID 17326046
  • B. Jones: The case for particle therapy. In: Br J Radiol. 79 (937), Jan 2006, pp. 24-31. Review. PMID 16421401
  • Hans Rinecker: Proton Therapy - New Opportunities for Cancer. Herbig, Munich 2005, ISBN 3-7766-2422-1 .
  • Boris Peter Selby, Georgios Sakas, Stefan Walter, Wolfgang-Dieter Groch, Uwe Stilla : Pose estimation of eyes for particle beam treatment of tumors. In: Image processing for medicine 2007. Springer-Verlag, Berlin / Heidelberg 2007, ISBN 978-3-540-71090-5 .

Individual evidence

  1. ^ U. Amaldi, G. Kraft: Radiotherapy with beams of carbon ions. In: Rep. Progr. Physics. 68, 2005, pp. 1861-1882.
  2. ^ O. Jäkel: State of the Art in Hadron Therapy. In: AIP Conf. Proc. 958, 1, 2007, p. 70.
  3. ↑ a b PTCOG: Particle Therapy Co-Operative Group Specialist working group on particle therapy
  4. ↑ Tagesschau contribution on November 2, 2009 for the opening ceremony of the Heidelberg Ion Beam Therapy Center (HIT)
  5. ↑ Topic of the day on November 1st, 2009 on the occasion of the upcoming opening of the Heidelberg Ion Beam Therapy Center (HIT) with an explanation of the particle therapy
  6. ^ Out of the particle therapy in Kiel. ( Memento from October 16, 2011 in the Internet Archive ) In: Kieler Nachrichten online. September 14, 2011.
  7. ^ West German Proton Therapy Center Essen (WPE). Retrieved March 14, 2017 .
  8. ↑ https://www.wpe-uk.de/ueber-uns/ . In: West German Proton Therapy Center Essen (WPE) . December 11, 2017 ( wpe-uk.de [accessed December 13, 2017]).
  9. ↑ a b Marburg Ion Beam Therapy Center
  10. ↑ National Institute of Radiological Sciences ( Memento from June 12, 2013 in the web archive archive.today )
  11. ↑ Hyogo Ion Beam Medical Center ( Memento from January 27, 2011 in the web archive archive.today )
  12. ↑ Heidelberg Ion Beam Therapy Center