<b>Electron beams and proton beams and alpha particles [helium nuclei]</b>, because of the nature of their particles, weighted and charged, do not penetrate as deeply or as widely as neutrons or gamma rays.  They are capable of delivering tumor directed radiation that is very focused.  Proton beams, because of the nature of the proton interaction-it gives up a major part of its energy just at or before the boundary of its excursion-is especially suited for getting at LMS tendril extensions.  For isolated tumors growing where it would be difficult to get clear margins, and where ablation [RFA or cryo] would not be possible, this might be the treatment of choice.

<b>Proton beam</b> treatment is available at several centers in the US.  However, currently, only Loma Linda and possibly the Boston site will deal with metastatic tumor, and then if it is not part of extensive disease.  

<b>Neutron Beam</b> treatment with high-energy neutrons has had some effect on large, difficult-to-treat LMS tumors of patients on the LMS list.  The Fermi Laboratory does this treatment.

<b>External Beam gamma ray - Fractionated Radiation Therapy</b> treatment involves exposure of normal tissue to the radiation.  It is given in a fraction of the total dose [usually 1/30th] at a time, so it is called fractionated [made into fractions].  In <b>hyperfractionated radiation therapy</b>, the daily dose is divided into smaller doses that are given more than once a day. The treatments usually are separated by 4 to 6 hours.  Besides the inconvenience, sometimes the toxicity is increased.  Ask to see references if this is offered to you.

<b>External Beam gamma ray - Three-dimensional conformal radiation therapy</b> is a radiation technique that is being used in some cancer centers. Computer simulation produces an accurate image of the tumor and surrounding organs so that multiple radiation beams can be shaped exactly to the contour of the treatment area. Because the radiation beams are precisely focused, nearby normal tissue is relatively spared. This technique is being used to treat prostate cancer, lung cancer, and certain brain tumors. 

<b>External Beam gamma ray - Stereotactic radiosurgery</b>, which uses gamma rays or a linear accelerator, is useful for treating certain kinds of brain tumors and some malformations in the brain's blood vessels. One technique, called the '<b>gamma knife</b>,' uses many powerful, precisely focused radiation beams. The patient wears a special helmet to focus the gamma rays and aim them at the target tissue from many directions. The treatment is painless and bloodless and, unlike conventional brain surgery, there is no danger of infection. Other systems use a linear accelerator to deliver the radiation in arcing paths around the patient's head.  Normal tissue is relatively spared.

<b>External Beam gamma ray - The cyberknife</b> is a new, but less common, treatment that is being used to treat brain tumors. This system uses a miniature radiation machine and a robotic arm that moves around the patient's head while delivering small doses of radiation from hundreds of directions. During treatment a computer analyzes hundreds of brain images and adjusts for slight movements by the patient. This makes it possible to deliver the treatment without using a frame to hold the patient's head still. Only the tumor receives the high doses of radiation and healthy tissue is relatively spared. 

<b>Intensity-modulated beam radiotherapy (IMRT)</b> delivers a highly conformal, three-dimensional (3-D) distribution of radiation doses that is not possible with conventional methods. IMRT allows for the treatment of multiple targets with different doses, while simultaneously minimizing radiation to uninvolved critical structures. With 3-D computerized dose optimization, IMRT is a vast improvement over the customary trial-and-error method of treatment planning.  It allows high doses of radiation to be delivered to tumor tissue while reducing radiation damage to healthy tissue.<br>&&url PMID: 10631687  