Proton beam therapy is similar to 3-Dimensional and cofnromal readiatherapy but it uses proton beams that are directed to the tumor. Protons are positive parts of atoms. Unlike x-rays, which are what conventional radiation emplys, protons release energy both before and after they hit their target. If interst to physicians, protons cause little damage to tissues they pass through and release their energy after traveling a certain distance.
The proponents of this novel therapy argue that this feature of proton Beam radiotherapy justifies its use. However, there are other ways to spare normal tissue, including: Three-dimensional conformal radiation therapy (3D-CRT. Intensity modulated radiation therapy (IMRT), Conformal proton beam radiation therapy, Stereotactic radiosurgery/stereotactic radiotherapy and Brachytherapy (internal radiotherapy). In addition, the claim that safety alone is the reason to adopt proton beam for routine use should not be made in the absence of studies that confirm better outcomes. Because proton beam technology is available on only a number of US facilities and because craniospinal radiation is not performed very frequently, studies to support the assertion that proton beam radiotherapy is superior have not been done and the treatment should still be considered investigational.
Proton beam therapy systems are approved by the FDA 510(k) process as a “medical device designed to produce and deliver a proton beam for the treatment of patients with localized tumors and other conditions susceptible to treatment by radiation” (FDA, 2006). Examples of such systems are the Optivus Proton Beam Therapy System (Optivus Technology Inc., Loma Linda, CA) and the IBA Proton Therapy System-Proteus 235 (Ion Beam Applications S.A., Philadelphia, PA).
The Agency for Healthcare Research and Quality published a 2009 technology report on particle beam radiation therapies for the treatment of cancers including skull base and brain tumors. They noted that there is a proposed advantage of using particle beam therapy, including PBT, where precise radiation targeting is critical in tumors of the skull base and tumors adjacent to the brain and brain stem. The report concluded that studies on charged particle therapy “do not document the circumstances in contemporary treatment strategies in which radiotherapy with charged particles is superior to other modalities. Comparative studies in general, and randomized trials in particular (when feasible) are needed to document the theoretical advantages of charged particle radiotherapy to specific clinical situations”.
In a technology assessment on the use of PBT for the treatment of cancer, the Australia and New Zealand Horizon Scanning Network (2006) stated that PBT “may be of particular benefit” in the treatment of patients with intermediate depth tumors such as those in the head, cancers that are located in difficult or dangerous-to-treat areas, and tumors in locations where “conventional radiotherapy would damage surrounding tissue to an unacceptable level” (e.g., central nervous system and head). PBT “may be ideal for use in the treatment of pediatric patients where the need to avoid secondary tumors is important due to the potentially long life span after radiation treatment when they may develop radiation induced malignancies. It is not clear how this may relate to cranio-spinal radiation.
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