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SUMMARY:Clinical Aspects of Proton Radiotherapy - Prof Tony Lomax\, Head o
 f Medical Physics\, Centre for Proton Radiation Therapy\, Paul Scherrer In
 stitute\, Switzerland
DTSTART:20090915T110000Z
DTEND:20090915T120000Z
UID:TALK18933@talks.cam.ac.uk
CONTACT:Mala Jayasundera
DESCRIPTION:Proton therapy is making the move out of the research laborato
 ry and into the clinic. New hospital based facilities in the US\, Asia and
  Europe testify to the growing interest in this treatment modality. Proton
 s have the advantageous characteristic that the energy from a mono-energet
 ic proton beam is deposited in a small region known as the Bragg peak\, be
 yond which the deposited dose is almost\, but not quite\, zero. Numerous c
 omparative treatment planning studies have shown the theoretical advantage
  for protons in a number of indications\, and the existing and new facilit
 ies are working towards translating this theoretical advantage into a real
  clinical advantage. \n\nIn order to make the essentially mono-energetic\,
  and narrow\, pencil beams that are emitted from proton accelerators usefu
 l for therapy\, the method most widely used is the so-called passive scatt
 ering technique. In this\, the narrow beam is widened through the use of s
 cattering elements\, whilst the narrow Bragg peak is extended in depth thr
 ough the application of a series of depth shifted and modulated Bragg peak
 s in order to form a so-called ‘Spread-Out-Bragg Peak’ (SOBP). The fin
 al form of the delivered field is defined by the use of field specific col
 limators and compensators\, the latter of which match the distal end of th
 e field to the distal extent of the target volume. \n\nCoupled with the de
 velopment of the new proton facilities is a growing interest in more sophi
 sticated delivery techniques. One such is active scanning\, in which narro
 w\, mono-energetic pencil beams are magnetically scanned throughout the ta
 rget volume under computer control. This approach has a number of potentia
 l advantages over the passive approach. It is very flexible\, makes more e
 fficient use of the available protons\, is more conformal than passive sca
 ttering\, results in lower secondary irradiations to the patient (i.e. neu
 tron background) and last\, but certainly not least\, allows for the deliv
 ery of Intensity Modulated Proton Therapy (IMPT)\, the proton equivalent o
 f IMRT. IMPT provides great flexibility in sculpting doses around complex 
 tumours and in the neighbourhood of multiple critical structures\, whilst 
 maintaining the inherent characteristic of proton therapy\, a substantial 
 reduction of dose to all non-target normal tissues. In treatment planning 
 comparisons\, this has been shown to be reduced by a factor of 2-6\, which
  could have a significant impact on late effects such as secondary tumour 
 induction. In addition\, it could also be expected that there may even be 
 (as yet undiscovered) advantages from proton therapy in terms of dose esca
 lation\, whereby the relatively steep dose gradients across critical struc
 tures could allow higher tolerance doses than are possible with other tech
 niques.\nIn summary\, the physical characteristics of protons dictate that
  for the same total dose to the tumour\, the dose to the surrounding norma
 l tissues will be reduced. As there is much evidence from past advances in
  radiotherapy that improved dose conformation and reduced normal tissue do
 ses improves outcomes\, then it is to be expected that proton therapy will
  bring similar advantages.\n
LOCATION:CRI Lecture Theatre
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