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Hospitals Look to a Nuclear Tool to Fight Cancer
The feed points us to a NYTimes article about hospitals using particle accelerators to treat cancer. While expensive, proponents say that the proton beams generated by the accelerators are more precise than conventional X-ray radiation therapy. This results in fewer side effects and reduced irradiation of surrounding tissue. The technology's critics say that the cost is not justified by a measurable increase in the level of care given to the patients. Nevertheless, this is an excellent example of "pure scientific research" leading to a useful, unrelated technique. From the NYTimes:
"Tumors in or near the eye, for instance, can be eradicated by protons without destroying vision or irradiating the brain. Protons are also valuable for treating tumors in brains, necks and spines, and tumors in children, who are especially sensitive to the side effects of radiation."
possibly, but I'd rather be bombarded with focused protons than barely focused gamma/x rays.
protons have very little penetration power due to their high weight and volume. Normal alpha particle emitters, for example, are blocked simply by the lining of dead skin covering your body. Goggles and standard clothing will protect you from anything short of eating the particles.
Since they are accelerated, I'm guessing they penetrate further, but they will be stopped quicker too (charge, mass, volume, all these will make them easier to stop than high energy photon radiation). Best of all, it's the stopping/slowing of the protons that kills the cells (they hit stuff, break stuff, and stop/slow down), so less energy will be needed since the majority of the high-energy photons would just pass through. The trickiest part would be to determine how many protons and with how much energy.
Self proclaimed typo king, and inventor of the bear destroying coffee table (patent not pending).
For more information on proton beam therapy, albeit from a provider's point of view, here is a link to Loma Linda's Proton therapy page. (They were the first to set up a proton therapy center.) In addition to static informational and historical pages, there are also some videos explaining what they have to offer and how it works.
By contrast, accelerated protons deposit their energy almost evenly, at a relatively low rate, until they are slowed to a certain energy, at which point their deceleration rapidly increases, accompanied by a massive increase in linear energy deposition. This leads to the "Bragg Peak", which offers a much, much more accurately targeted beam than is possible with conventional sources. (See this illustration as an example - compare the red line (in this case, C12 ions, but a similar principle) to the green line (an 18MeV photon beam). By carefully tuning the beam energy and orientation this point can be scanned over the tumour volume, giving a very localised dose deposition.
What puzzles me is why this is news - I was under the impression that this concept is well-established, and has been fairly well verified already. Just some fluff to fill up the science and medicine section, maybe? Now if it was about the CERN anti-proton tests, that's certainly something with a more dubious cost/benefit analysis...
* - I say a few assumptions, these are basically the principle ones behind all radiotherapy - that is, that all dose at the end of track structures is created equal and all dose is bad according to the LNT. While these ideas may not be strictly true, it is unlikely for them to be so wrong that it would invalidate the treatment as a whole.
For a nice picture of energy deposition vs. depth see e.g. http://www.gsi.de/forschung/bio/energy_e.html
One can adjust the peak energy deposition's depth by varying the proton's energy. The surrounding tissue gets a much lower dose than in X-Ray irradiations.
Combine the particle accelerator with a PET (http://en.wikipedia.org/wiki/Positron_emission_tomography) and you can irradiate a cancer with cubic millimeter resolution.
This is actually not a new, purely academic technique, it is already commercially available, see http://en.wikipedia.org/wiki/Proton_therapy
Attention: I'm not a doctor but a physics student :)
One thing: http://www.gsi.de/forschung/bio/energy_e.html is actually about heavy ions (carbon). The curve is not _too_ different for a proton, though.
Well the University of Ghent is one of the most advanced oncology research centers... I guess what's new is not the method itself, but the fact that hospitals are starting to buy these (for operating leverage?)...
TFA is all about:
The relatively recent decision of some hospitals (and some entities that are set up to minimize economic risk rather than just do healthcare) to build a surprisingly large number of these very expensive, rather limited machines and
The lack of good science to suggest that, for most cancers, this technology is not any better than the older (still advanced, still expensive) gamma and x-ray treatments.
To my mind, the biggest WTF in the entire article is Medicare's decision to pay more for the proton beam therapy than the older ones, before solid information is available to say that it does or does not work any better than other therapies . You create a huge financial opportunity for investors without much in the way of benefit for society at large. The highway of modern medicine is littered with the personal and financial wrecks of treatments, medicines and ideas that seemed like a great idea at the time (else why do them) but turned out to work either less well than before or simply were much more expensive without significant clinical benefit.
Faster! Faster! Faster would be better!
This whole suggestion that Medical treatment with particle accelerators is new is not true. The use of such machines is stock medical stuff and has been so for more than 20 years. As to side effects, here is what my mother was told just after she drank some I-131 made in the local accelerator... In response to her question about cancer risk, she was told, "We don't think you will live that long."
The use of focused beams to shoot tumors is also 20 years old or more. The use of the beams to make Gama, X and even Neutron or Positron beams is not new as well. Sorry no news here folks! The Slashdot people got hornswoggled!
Never Politically Correct ~ I prefer the facts If you don't like what I say, get a life, or comment yourself.
For breast cancer the story is even better. The longterm survival rates for most breast tumors is identical between a masectomy and radiation. Bonus with radiation is: you give some dose to the surrounding tissues potentially killing secondary malignancies, and of course the woman still has a breast. The best treatment as far as survival goes is a lumectomy but this usually can only be done early stage (hence all the focus on breast screening).
Proton therapy has some potential, however, the main articles claim that protons are accurant where as X-rays are inaccurant is miss leading/wrong. Protons don't penetrate as far into tissue. Thus the radiation is more targetted for superficial treatments. However, the opposite is the case for treatment at depth. Since the protons deposit their energy relatively close to the surface, you'd need a much higher total dose to treat an internal organ then with X-rays. It really would depend on the malignancy and how much you want to spread the radiation over. Different types of radiation (and different energy levels, ie. 6MeV X-rays, 15 MeV X-rays), have different dose build up and fall off profiles. It really depends on where the tumor is which one will be the best.
In typical clinical process there is the point of interest (POI) and the target volume. These differ and sometimes by a wide margin. The target (ie where the radiation actually goes) is larger than the actual area that the oncologist thinks localizes the tumor. This is to allow for alignment errors (patient moves, machine tolerances etc), plus a safety margin (typically around 7mm) to try to get the stray cancer cells around the tumor. Anyways, the physician will prescribe a certain dose at a point in the target, and a percentage at a isosurface, so say 1000 Cy, 80% at POI + 7mm. At any rate you may not use the accuracy because you want some dose "off target" for localized tumor control (as apposed to general tumor control that you attempt with chemo).
X-ray treatment machines are much more accurate than claimed. Modern treatment units have among other things MLC (multi leaf collimaters) to shape the beam. You can thing of the beam like a light bulb, they place a bunch of retangular peices of metal between the patient and the bulb to get the desired shape. These are dynamically tuned so at one angle you might get 20% of the dose at a particular shape, and the rest at a different shape say, or they can be in motion during the "beam on" painting a more uniform distribution. At anyrate, a variety of angles (now in the works to use continuous arcs as well), and leaf positions enable you to paint the target with the 3 dimensional dose distribution you want with about 3mm spatial accuracy (add ins/some systems out of the box have about 5mm accuracy even after accounting for breathing in realtime on say a lung tumor), while spreading out the dose along the healthy tissue which reduces risk to the other areas. Also, newer machines can get an add on for about 600k that will enable the unit to act as a CT scanner (typical price 2-4M),