Page 46 - 2014 Printable Abstract Book
P. 46
as a product of the absorbed dose and the RBE, has to be calculated in a treatment planning system (TPS)
of C-ion radiotherapy. At NIRS, a pragmatic biological model, based on in-vitro response of human salivary
gland (HSG) cell and clinical experience from fast neutron radiotherapy, has been developed and utilized
in passively scattered C-ion radiotherapy. The RBE values derived from the clinical results for non-small
cell lung cancer in terms of tumor control probability (TCP) appeared to be consistent with the RBE values
predicted based on the model. Recently, we have developed a new irradiation method, i.e., a pencil beam
scanning method, and started clinical treatments since 2011 for further development of C-ion
radiotherapy. On this occasion, the biological model in the TPS was upgraded to reflect the physical and
biological characteristics of the therapeutic C-ion beam more accurately in prediction of the RBE. The new
model had to be built on the technical continuity with the conventional biological model to succeed its
promising clinical results, as well as to enable the possible future modifications and adaptations for
scanning irradiation method. The new model offers versatile estimation of the biological effectiveness of
various radiations based on their microdosimetric information, while harmonizing with the original
approach. An outline of the biological models used in the TPS at NIRS and its applications will be presented
in the meeting.
(S703) Proton beam radiotherapy: What have we learned in 40 years and where to we go from here?
Reinhard Schulte, Loma Linda University, Loma Linda, CA
Proton beam radiotherapy started on a larger scale during the mid-1970s with the first clinical
proton treatment program for fractionated radiation therapy of tumors developed at the Harvard
Cyclotron by Dr. Herman Suit and his colleagues from the Massachusetts General Hospital. To understand
the potential clinical role of proton beam radiotherapy in the future, it is instructive to look at its historical
development. From the first suggestion that protons provide main advantages compared to photons due
to the Bragg peak effect, suggested by then Harvard physicist Robert Wilson in 1947, to the opening of
the first proton treatment center in Loma Linda, California in 1990, it took more than 40 years. Many
factors have contributed to this relatively slow development, among which are lack of appropriate 3D
imaging and computer technology, high initial capital costs of protons, and the lack of convincing clinical
data. These challenges are, to some degree, still present today. The first milestone that had to be reached
to make clinical proton applications feasible was computed tomography. Only then could treatment
planning and image guidance techniques be developed. Equally important was that first convincing clinical
data were published by the MGH/Harvard team for base of skull and ocular melanoma tumor sites, which
led to the well-established clinical indications for proton therapy today. The proton treatment facility at
Loma Linda University Medical Center was the first large-scale clinical proton treatment program in the
world and more than 18,000 patients have been treated since its inception, including about 1,000
pediatric patients. Other clinical facilities at larger academic centers followed during the first decade of
st
the 21 century. The clinical proton radiotherapy experience, which has accumulated during the first 15
years at the Harvard cyclotron and now over 20 years in the hospital setting, shows that protons lead to
good clinical outcomes. In order to secure a future for proton beam therapy, however, it will important
to (1) make ancillary technology of treatment planning and image guidance used with proton therapy
compatible to that used with modern photon treatment Technologies, including biological weighting,
IMPT, and minimization of range uncertainties; (2) to demonstrate for which clinical indications or patient
subsets protons have a clear dosimetric advantage; and (3) to perform randomized clinical trials where
44 | P a g e
of C-ion radiotherapy. At NIRS, a pragmatic biological model, based on in-vitro response of human salivary
gland (HSG) cell and clinical experience from fast neutron radiotherapy, has been developed and utilized
in passively scattered C-ion radiotherapy. The RBE values derived from the clinical results for non-small
cell lung cancer in terms of tumor control probability (TCP) appeared to be consistent with the RBE values
predicted based on the model. Recently, we have developed a new irradiation method, i.e., a pencil beam
scanning method, and started clinical treatments since 2011 for further development of C-ion
radiotherapy. On this occasion, the biological model in the TPS was upgraded to reflect the physical and
biological characteristics of the therapeutic C-ion beam more accurately in prediction of the RBE. The new
model had to be built on the technical continuity with the conventional biological model to succeed its
promising clinical results, as well as to enable the possible future modifications and adaptations for
scanning irradiation method. The new model offers versatile estimation of the biological effectiveness of
various radiations based on their microdosimetric information, while harmonizing with the original
approach. An outline of the biological models used in the TPS at NIRS and its applications will be presented
in the meeting.
(S703) Proton beam radiotherapy: What have we learned in 40 years and where to we go from here?
Reinhard Schulte, Loma Linda University, Loma Linda, CA
Proton beam radiotherapy started on a larger scale during the mid-1970s with the first clinical
proton treatment program for fractionated radiation therapy of tumors developed at the Harvard
Cyclotron by Dr. Herman Suit and his colleagues from the Massachusetts General Hospital. To understand
the potential clinical role of proton beam radiotherapy in the future, it is instructive to look at its historical
development. From the first suggestion that protons provide main advantages compared to photons due
to the Bragg peak effect, suggested by then Harvard physicist Robert Wilson in 1947, to the opening of
the first proton treatment center in Loma Linda, California in 1990, it took more than 40 years. Many
factors have contributed to this relatively slow development, among which are lack of appropriate 3D
imaging and computer technology, high initial capital costs of protons, and the lack of convincing clinical
data. These challenges are, to some degree, still present today. The first milestone that had to be reached
to make clinical proton applications feasible was computed tomography. Only then could treatment
planning and image guidance techniques be developed. Equally important was that first convincing clinical
data were published by the MGH/Harvard team for base of skull and ocular melanoma tumor sites, which
led to the well-established clinical indications for proton therapy today. The proton treatment facility at
Loma Linda University Medical Center was the first large-scale clinical proton treatment program in the
world and more than 18,000 patients have been treated since its inception, including about 1,000
pediatric patients. Other clinical facilities at larger academic centers followed during the first decade of
st
the 21 century. The clinical proton radiotherapy experience, which has accumulated during the first 15
years at the Harvard cyclotron and now over 20 years in the hospital setting, shows that protons lead to
good clinical outcomes. In order to secure a future for proton beam therapy, however, it will important
to (1) make ancillary technology of treatment planning and image guidance used with proton therapy
compatible to that used with modern photon treatment Technologies, including biological weighting,
IMPT, and minimization of range uncertainties; (2) to demonstrate for which clinical indications or patient
subsets protons have a clear dosimetric advantage; and (3) to perform randomized clinical trials where
44 | P a g e
