gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Assessment of relative merits of proton and carbon ion beam therapy

Meeting Abstract

  • H. Suit - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • B. Clasie - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • T. DeLaney - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • J. Flanz - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • L. Gerweck - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • S. Goldberg - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • H. Kooy - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • A. Niemierko - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • H. Paganetti - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA
  • A. Trofimov - Radiation Oncology, Mass General Hospital. Harvard Medical School, Boston, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog194

DOI: 10.3205/09ptcog194, URN: urn:nbn:de:0183-09ptcog1945

Published: September 24, 2009

© 2009 Suit et al.
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Outline

Text

Objectives: Assess efficacy of proton and carbon ion therapy.

Methods: Evaluate the rationale, physical, biological and clinical data base for 1H and 12C therapy.

Results: The bases for interest in 1H and 12C therapy are the potential of: superior dose distributions for nearly all sites and the high LET and RBE of 12C beams. The superior dose distributions are based on the finite range of these particle beams; that range is dependent on the initial energy and tissue density. 12C ion beams have a narrower penumbra. Clinical beams are designed to provide a biologically equivalent dose [BED] distribution across the depth of interest as defined by the treatment plan. Particle therapy using gantry equipped machines have the same flexibility as X-ray therapy, viz beam number, direction, intensity modulation etc. For 12C therapy, design vhof the physical dose distribution is more complex due to the substantial variation of RBE with LET, dose/fraction, cell type, etc.

A large question is the impact of high LET/RBE on the clinical efficacy. Fast neutron beams have near comparable LET and RBE to clinical 12C beams. A historical fact is that the outcomes of x ray and neutron therapy based on beams of similar depth dose characteristics have been interpreted as yielding unacceptable rates of serious treatment related injury. Significantly, of 8 US neutron therapy centers, 5 have closed and there are now only two active centers in Europe.

1H therapy has been administered with low dose /fraction [except for uveal melanoma] and 12C with high dose/fraction. Analysis of the reported results of 1H and 12C therapy are to be discussed in terms of local control vs Grade-III complications. At present, the outcome reports indicate that there may be an advantage for 12C for irradiation of chordoma of the skull base and sacrum, stage I NSCLC, H/N mucosal melanoma and renal cancer. Protons appear to be at least as effective as 12C for chondrosarcoma of skull base, uveal melanoma, H/N squamous cell carcinoma, sinus adenocystic carcinoma and hepatocellular carcinoma. 12C therapy dose levels have been high in terms of BED, as treatment has been hypofractionated [2-20 fractions], and high total doses. Even so, reported complication rates have been modest.

Conclusions: Our assessment is that the most effective treatment strategy might be low LET 1H for the CTV and high LET 12C for the boost dose. 12C would be used at low dose/fraction, viz ~ 2 Gy(RBE)/fraction so as to employ the highest feasible RBE. The total time and fraction number would be comparable to current proton therapy. Assessment of the clinical efficacy of 12C vs 1H therapy needs data from clinical trials of 1H vs 12C or 1H combined with 12C. The tumor types and stages would preferably be those for which the TCP by 1H is in the 20-70% range, viz the steepest section of the dose response curve.