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Medical Forum / Diseases and Disorders / Prostate Cancer / May 2008HDR Brachytherapy, Cyberknife, and nerve sparing
I consulted with Dr. Demanes (www.cetmc.com) about HDR brachytherapy (temporary Iridium-192 implants). Has anyone here been treated by him, and how was the experience if so? He did indicate sexual SE rate could be up to 50%; other SEs less than with permanent seeds due to precision. This is the only type of treatment he offers (with or without external beam). He could not quantify the risk of secondary cancers resulting from HDR monotherapy radiation exposure. Has anyone consulted at Stanford Univ. about Cyberknife for PCa? Any comparisons in ability to spare healthy tissue between these two? Is there any such thing as some "nerve sparing" capability when it comes to PCa radiation therapy as with ideally-performed surgery, or is it less controllable? Can nerves heal if damaged by radiation, or is this irreversible? It seems that the disclosure of such SEs all hover around 50% regardless of treatment method. Thanks. > ... He could not quantify the risk of secondary > cancers resulting from HDR monotherapy radiation exposure. I don't know if anyone has solid data on secondary cancers due to radiation. The first studies of this simply looked at Japanese atom bomb victims and attempted to correlate cancer incidence with radiation exposure. It was not a very accurate method. There have been more studies since which you can find on PubMed. It is my recollection that the risk is small, but not zero. As for various types of radiation, that's probablys till anyone's guess. > Is there any such thing as some "nerve sparing" capability when it > comes to PCa radiation therapy as with ideally-performed surgery, or > is it less controllable? You need to ask the rad onc about this. My rad onc told me that she was able to spare the urethra during my HDR brachytherapy, which sounds like they do have significant amounts of targetting control. However "sparing" is partly a matter of what needs to be treated. If the cancer is near or around the nerves, I wouldn't expect a good treatment plan to be very sparing. > Can nerves heal if damaged by radiation, or > is this irreversible? Again, a good question for the rad onc. Please let us know if he answers. > It seems that the disclosure of such SEs all > hover around 50% regardless of treatment method. I get the feeling that the docs don't really know what to say and so give an answer that can't be easily refuted. I also was given the 50% estimate. I would say that, in my case, the immediate effects were small. Now, four years later, they seem larger. But then I'm four years older. Maybe that accounts for the difference, not the treatment. Alan > Is there any such thing as some "nerve sparing" capability when it > comes to PCa radiation therapy as with ideally-performed surgery, or > is it less controllable? Can nerves heal if damaged by radiation, or > is this irreversible? It is my understanding that radiation does not damage nerves. This is due to the fact that radiation kills cell only when they divide. Since nerve cells rarely divide, they are not effected by radiation. However, some degree of ED can be experienced by radiation due to damage to the small blood vessels. However, this is exactly the type of ED that makes Viagra an effective treatment. John > It is my understanding that radiation does not damage nerves. This is > due to the fact that radiation kills cell only when they divide. Radiation given in sufficiently strong doses will damage or kill any type of cell. However, I think the radiation oncologists attempt to produce a dose that is as precisely balanced as possible to damage the DNA by ionization (i.e., knocking electrons off the atoms in the DNA) so that normal cell repair functions will take more time than the cell has before the cell attempts to divide - using the damaged DNA. Cancer cells are especially susceptible to radiation because 1) they divide frequently and 2) they already have damaged DNA (which is why they are cancerous) and already have poorly functioning or non-functioning DNA repair mechanisms. At any rate, that's my unqualified speculation about how this works. We need a rad onc or physical biologist to give us an authoritative explanation. > Since > nerve cells rarely divide, they are not effected by radiation. [quoted text clipped - 3 lines] > > John I have found that Viagra does help - though I don't know if what I have is really radiation induced or just the effects of aging. Alan |
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