Page 45 - 2014 Printable Abstract Book
P. 45
S06 PROTRON AND HEAVY ION BEAM THERAPY
The clinical merits and cost-effectiveness of cancer radiotherapy using protons or carbon ions are
under intense scrutiny in the international radiation oncology community. This symposium will address
emerging treatment-planning optimization approaches, and the impressive clinical outcomes that have
been achieved.
(S701) Treatment planning approaches for using RBE in radiotherapy: from carbon ions to protons.
Thomas Friedrich; Rebecca Grün; Marco Durante; and Michael Scholz, GSI Darmstadt, Darmstadt,
Germany
Understanding the larger biologic effects after charged particle irradiation in comparison to
photons is of importance for particle therapy. The high relative biological effectiveness (RBE) of carbon
ions is one of the rationales for their use in carbon therapy. For treatment planning (TP) knowledge of RBE
is mandatory and must be either obtained from experiments or clinical studies or predicted by RBE
modeling. In the Japanese facilities an approach is used where the clinical RBE is estimated based on
experimental or simulated in-vitro RBE values for 10% survival of HSG cells in combination with the clinical
experience with neutron beams. In European facilities the Local Effect Model in its original version is used
[1]. There the RBE is obtained based on the biological effects after photon irradiation, taking into account
dose, LET and depth dependence and the irradiated tissue or cell type. In the talk, insight in the concepts
and applications of the LEM as used in the clinics and in its recent improved version [2, 3] is given.
Emphasis is put on conceptual differences to other models and the link between the RBE data and the TP
system. The observed systematic dependencies of RBE would also be expected for protons where RBEs in
general are smaller, but in current clinical practice the RBE is considered constant as 1.1. In recent years
an increasing number of publications from both medical physicists and radiobiologists challenged this
‘fixed RBE concept’. Thus a transfer of what is known from carbon ions to protons is desirable. While the
clinical impact remains unclear, radiobiological experiments and modeling consistently suggest significant
deviations from 1.1, and the higher RBE would cause a larger effective range. In the talk a review of the
strategies to understand and predict the systematics of proton RBE for the use in TP is given and
implications of the LEM [4] are discussed in relation to results from different models. Finally current open
questions in TP which are related to RBE are considered for proton and carbon therapy, demonstrating
the persisting relevance of RBE modeling in particle therapy. [1] Scholz et al., Radiat. Environ. Biophys. 36,
59 (1997) [2] Elsässer et al., Int. J. Radiat. Oncol. Biol. Phys. 78, 1177 (2010) [3] Friedrich et al., Int. J. Radiat.
Biol. 88, 103 (2012) [4] Grün et al., Med. Phys. 40, 1716 (2013)
(S702) Treatment Planning Approaches for Using RBE in Carbon Ion Radiotherapy at NIRS. Taku Inaniwa,
National Institute of Radiological Sciences, Chiba, Japan
Advantageous depth-dose profile of carbon-ion (C-ion) beam as well as its increasing relative
biological effectiveness (RBE) toward the Bragg peak renders C ions attractive for treating deep-seated
tumors. Following pioneering works at Lawrence Berkeley Laboratory in the United States, National
Institute of Radiological Sciences (NIRS) in Japan started C-ion radiotherapy since 1994 with the Heavy Ion
Medical Accelerator in Chiba (HIMAC). Promising clinical results in the past 20 years at NIRS proved that
C-ion radiotherapy offers a significant anti-tumor effect with acceptable toxicities in surrounding normal
tissues. To make optimal use of the advantageous characteristics of C ions, a clinical dose, which is defined
43 | P a g e
The clinical merits and cost-effectiveness of cancer radiotherapy using protons or carbon ions are
under intense scrutiny in the international radiation oncology community. This symposium will address
emerging treatment-planning optimization approaches, and the impressive clinical outcomes that have
been achieved.
(S701) Treatment planning approaches for using RBE in radiotherapy: from carbon ions to protons.
Thomas Friedrich; Rebecca Grün; Marco Durante; and Michael Scholz, GSI Darmstadt, Darmstadt,
Germany
Understanding the larger biologic effects after charged particle irradiation in comparison to
photons is of importance for particle therapy. The high relative biological effectiveness (RBE) of carbon
ions is one of the rationales for their use in carbon therapy. For treatment planning (TP) knowledge of RBE
is mandatory and must be either obtained from experiments or clinical studies or predicted by RBE
modeling. In the Japanese facilities an approach is used where the clinical RBE is estimated based on
experimental or simulated in-vitro RBE values for 10% survival of HSG cells in combination with the clinical
experience with neutron beams. In European facilities the Local Effect Model in its original version is used
[1]. There the RBE is obtained based on the biological effects after photon irradiation, taking into account
dose, LET and depth dependence and the irradiated tissue or cell type. In the talk, insight in the concepts
and applications of the LEM as used in the clinics and in its recent improved version [2, 3] is given.
Emphasis is put on conceptual differences to other models and the link between the RBE data and the TP
system. The observed systematic dependencies of RBE would also be expected for protons where RBEs in
general are smaller, but in current clinical practice the RBE is considered constant as 1.1. In recent years
an increasing number of publications from both medical physicists and radiobiologists challenged this
‘fixed RBE concept’. Thus a transfer of what is known from carbon ions to protons is desirable. While the
clinical impact remains unclear, radiobiological experiments and modeling consistently suggest significant
deviations from 1.1, and the higher RBE would cause a larger effective range. In the talk a review of the
strategies to understand and predict the systematics of proton RBE for the use in TP is given and
implications of the LEM [4] are discussed in relation to results from different models. Finally current open
questions in TP which are related to RBE are considered for proton and carbon therapy, demonstrating
the persisting relevance of RBE modeling in particle therapy. [1] Scholz et al., Radiat. Environ. Biophys. 36,
59 (1997) [2] Elsässer et al., Int. J. Radiat. Oncol. Biol. Phys. 78, 1177 (2010) [3] Friedrich et al., Int. J. Radiat.
Biol. 88, 103 (2012) [4] Grün et al., Med. Phys. 40, 1716 (2013)
(S702) Treatment Planning Approaches for Using RBE in Carbon Ion Radiotherapy at NIRS. Taku Inaniwa,
National Institute of Radiological Sciences, Chiba, Japan
Advantageous depth-dose profile of carbon-ion (C-ion) beam as well as its increasing relative
biological effectiveness (RBE) toward the Bragg peak renders C ions attractive for treating deep-seated
tumors. Following pioneering works at Lawrence Berkeley Laboratory in the United States, National
Institute of Radiological Sciences (NIRS) in Japan started C-ion radiotherapy since 1994 with the Heavy Ion
Medical Accelerator in Chiba (HIMAC). Promising clinical results in the past 20 years at NIRS proved that
C-ion radiotherapy offers a significant anti-tumor effect with acceptable toxicities in surrounding normal
tissues. To make optimal use of the advantageous characteristics of C ions, a clinical dose, which is defined
43 | P a g e
