WEBVTT - How Proton Therapy Works 0:00:00.520 --> 0:00:03.840 Welcome to Brainstuff from how Stuff Works dot com where 0:00:03.840 --> 0:00:15.319 smart Happens. I am Marshall Brain with today's question, what 0:00:15.520 --> 0:00:19.160 is proton therapy and how does it work? Imagine that 0:00:19.200 --> 0:00:22.360 you were to be diagnosed with something like breast cancer, 0:00:22.520 --> 0:00:26.840 brain cancer, or prostate cancer. Up until now, your options 0:00:26.840 --> 0:00:31.280 have been fairly limited and fairly uncomfortable. The most common 0:00:31.320 --> 0:00:34.920 first line of attack is surgery. A surgeon cuts out 0:00:34.960 --> 0:00:37.920 the tumor as best he or she can. In the 0:00:38.000 --> 0:00:41.400 case of breast, brain, and prostate cancer, this approach can 0:00:41.400 --> 0:00:44.760 be fairly problematic. In the case of breast cancer, a 0:00:44.800 --> 0:00:47.360 woman may lose one or both of her breasts. In 0:00:47.400 --> 0:00:50.080 the case of brain cancer, parts of the brain can 0:00:50.120 --> 0:00:52.560 be damaged in the process of getting to the tumor, 0:00:52.960 --> 0:00:55.760 or the tumor may not be accessible at all. In 0:00:55.920 --> 0:01:00.000 prostate cancer, the patient is often left incontinent and impotent. 0:01:00.040 --> 0:01:04.559 In surgery is usually followed by chemotherapy to kill any 0:01:04.640 --> 0:01:09.399 remaining cancer cells. Chemotherapy is a drug cocktail that is 0:01:09.520 --> 0:01:13.520 in essence poison. The poison kills the cancer cells by 0:01:13.560 --> 0:01:17.440 targeting cells that reproduce rapidly. The side effect is that 0:01:17.560 --> 0:01:20.520 other cells in the body that happen to reproduce rapidly 0:01:20.880 --> 0:01:24.240 like hair follicles, and the cells lining the stomach often 0:01:24.319 --> 0:01:28.000 suffer as well. This explains the hair loss and nausea 0:01:28.360 --> 0:01:33.480 that often accompanies chemotherapy. Another possibility is X ray therapy, 0:01:33.520 --> 0:01:36.680 where multiple beams of X rays penetrate the body and 0:01:36.800 --> 0:01:40.360 intersect at the tumor. The tumor receives a high enough 0:01:40.400 --> 0:01:43.800 dose of X rays to damage the cancerous DNA and 0:01:43.959 --> 0:01:47.720 kill the cancer cells, but there can be collateral damage 0:01:47.760 --> 0:01:50.360 at the places where the X ray beams enter the 0:01:50.400 --> 0:01:54.280 body and overshoot the tumor. Healthy tissue near a tumor 0:01:54.360 --> 0:01:58.520 often gets damaged as well. There are other therapies, including 0:01:58.600 --> 0:02:02.920 bits of radioactive serial commonly called seeds, embedded in and 0:02:02.960 --> 0:02:05.600 around the tumor in the hope of killing the tumor 0:02:05.680 --> 0:02:10.639 with nuclear radiation, various new and experimental drugs targeting things 0:02:10.720 --> 0:02:13.880 like tumor blood supply, and so on. Most of the 0:02:13.919 --> 0:02:16.640 techniques in use today have side effects that can be 0:02:16.760 --> 0:02:20.320 quite unfortunate for the patient. This is why so many 0:02:20.400 --> 0:02:24.520 people are getting excited about proton therapy. The idea here 0:02:24.639 --> 0:02:28.400 is to use protons, which have been accelerated to near 0:02:28.560 --> 0:02:32.600 light speed in a particle accelerator to kill cancer tumors. 0:02:33.120 --> 0:02:36.680 The advantage of proton therapy is a good success rate 0:02:36.720 --> 0:02:40.120 with a low incidence of side effects. So what is 0:02:40.160 --> 0:02:43.200 a proton? If you think of a hydrogen atom, the 0:02:43.280 --> 0:02:46.440 proton is the some atomic particle at the core of 0:02:46.440 --> 0:02:50.320 the atom. A normal hydrogen atom has an electron orbiting 0:02:50.360 --> 0:02:54.240 that proton. By stripping off the electron and leaving behind 0:02:54.280 --> 0:02:57.840 a bare hydrogen nucleus, you have a proton that can 0:02:57.880 --> 0:03:01.880 be used for proton therapy. Protons are so small that 0:03:01.960 --> 0:03:04.799 they can fly through the body doing very little damage, 0:03:05.160 --> 0:03:07.280 but they do slow down as they make their way 0:03:07.320 --> 0:03:11.440 through tissue. Eventually, the protons come to a stop. Add 0:03:11.520 --> 0:03:15.120 or near the stopping point, protons strip electrons off of 0:03:15.200 --> 0:03:19.560 nearby atoms, changing important molecules in the process. If a 0:03:19.639 --> 0:03:23.640 doctor delivers enough protons to a tumor, cells inside the 0:03:23.680 --> 0:03:28.560 tumor die because of this electron activity. Some doctors described 0:03:28.600 --> 0:03:32.680 protons as acting like a firecracker, avoiding damage to tissue 0:03:32.760 --> 0:03:36.920 surrounding the tumor, but exploding inside the tumor. The reason 0:03:37.040 --> 0:03:40.160 is that protons do damage when they come to rest, 0:03:40.800 --> 0:03:43.560 So if they come to rest inside the tumor. The 0:03:43.640 --> 0:03:46.840 tumor is the only thing to get significant damage from 0:03:46.880 --> 0:03:50.800 the protons. The depth that the protons penetrate into the 0:03:50.840 --> 0:03:54.520 body can be controlled by their speed. Compared to X 0:03:54.640 --> 0:03:58.000 ray therapy, there is no exit dose that can harm 0:03:58.120 --> 0:04:01.320 healthy tissue beyond the tumor, and there's only a very 0:04:01.360 --> 0:04:05.680 small entry dose. The two big problems with proton therapy 0:04:05.800 --> 0:04:08.280 right now are the fact that it is so new 0:04:08.640 --> 0:04:12.080 and the cost. There are only a handful of proton 0:04:12.200 --> 0:04:15.240 therapy facilities in the United States at the moment, and 0:04:15.320 --> 0:04:19.919 these facilities are incredibly expensive, costing hundreds of millions of 0:04:19.960 --> 0:04:23.240 dollars to build. The cost is coming from the need 0:04:23.360 --> 0:04:27.880 for a complete, highly sophisticated particle accelerator at each facility. 0:04:28.320 --> 0:04:32.040 The particle accelerator creates the protons and then accelerates them 0:04:32.080 --> 0:04:35.800 to the precise speed needed to reach the tumor. Another 0:04:35.880 --> 0:04:39.640 problem is the high number of visits. A typical prostate 0:04:39.720 --> 0:04:43.640 cancer tumor might require forty daily visits to a proton 0:04:43.800 --> 0:04:47.880 therapy facility over the course of two months, unless you 0:04:47.920 --> 0:04:50.760 happen to live in the rare city that has a facility. 0:04:51.200 --> 0:04:54.760 This means a long daily commute or a two month 0:04:54.800 --> 0:04:58.480 hotel stay along with the cost of the forty sessions, 0:04:58.520 --> 0:05:01.440 which can rise into the pends of thousands of dollars. 0:05:02.080 --> 0:05:05.720 The hope is that technological advances will lower the cost 0:05:05.839 --> 0:05:09.680 of new facilities, making the treatment much more accessible and 0:05:09.800 --> 0:05:13.679 less expensive. If that happens, it could open a new 0:05:13.760 --> 0:05:19.000 era in cancer treatment. 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