The future of RT, according to Harvard Medical school

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Coming technical advances in radiation oncology][Article in German]

Suit H.

Department of Radiation Oncology, Massachusetts General Hospital,

Harvard Medical School, Boston, MA 02114, USA.

PURPOSE: To review the current limits on the efficacy of

radiotherapy (RT) due to technical factors and to assess the

potential for major improvements in technology. METHODS AND

MATERIALS: The method of this review was to assess the efficacy of

current RT in general terms; strategies for improving RT; historical

record of technological advances; rationale for further reductions

of treatment volume; and importance of defining and excluding

nontarget tissues from the target volume. The basis for the interest

in proton beam RT is developed, and the relative dose distributions

of intensity-modulated radiotherapy (IMRT) and intensity-modulated

proton RT (IMPT) are discussed. The discovery of the proton and the

first proposal that protons be used in RT is described. This is

followed by a brief mention of the clinical outcome studies of

proton RT. Likely technical advances to be integrated into advanced

proton RT are considered, specifically, four-dimensional treatment

planning and delivery. Finally, the increment in cost of some of

these developments is presented. RESULTS: For definitive RT, dose

limits are set by the tolerance of normal tissues/structures

adjacent or near to the target. Using imaging fusion of CT, MRI,

positron emission tomography, magnetic resonance spectroscopic

imaging, and other studies will result in improved definition of the

target margins. Proton beams are likely to replace photon beams

because of their physical characteristics. Namely, for each beam

path, the dose deep to the target is zero, across the target it is

uniform, and proximal to the target it is less. Proton therapy can

use as many beams, beam angles, noncoplanar, and dynamic, as well as

static, intensity modulation, as can photon plans. The ability for

much greater accuracy in defining the target position in space and

then maintaining the target in a constant position in the radiation

beam despite target movement between and during dose fractions will

be possible. The cost of proton RT will be modestly higher than

comparable high technology photon therapy. CONCLUSION: The

technology of RT is clearly experiencing intense and rapid technical

developments as pertains to treatment planning and dose delivery. It

is predicted that radical dose RT will move to proton beam

technology and that the treatment will be four dimensional (the

fourth dimension is time). The impact will be higher tumor control

probability and reduced frequency and severity of treatment-related

morbidity.