1 00:00:00,520 --> 00:00:03,840 Speaker 1: Welcome to Brainstuff from how Stuff Works dot com where 2 00:00:03,840 --> 00:00:15,319 Speaker 1: smart Happens. I am Marshall Brain with today's question, what 3 00:00:15,520 --> 00:00:19,160 Speaker 1: is proton therapy and how does it work? Imagine that 4 00:00:19,200 --> 00:00:22,360 Speaker 1: you were to be diagnosed with something like breast cancer, 5 00:00:22,520 --> 00:00:26,840 Speaker 1: brain cancer, or prostate cancer. Up until now, your options 6 00:00:26,840 --> 00:00:31,280 Speaker 1: have been fairly limited and fairly uncomfortable. The most common 7 00:00:31,320 --> 00:00:34,920 Speaker 1: first line of attack is surgery. A surgeon cuts out 8 00:00:34,960 --> 00:00:37,920 Speaker 1: the tumor as best he or she can. In the 9 00:00:38,000 --> 00:00:41,400 Speaker 1: case of breast, brain, and prostate cancer, this approach can 10 00:00:41,400 --> 00:00:44,760 Speaker 1: be fairly problematic. In the case of breast cancer, a 11 00:00:44,800 --> 00:00:47,360 Speaker 1: woman may lose one or both of her breasts. In 12 00:00:47,400 --> 00:00:50,080 Speaker 1: the case of brain cancer, parts of the brain can 13 00:00:50,120 --> 00:00:52,560 Speaker 1: be damaged in the process of getting to the tumor, 14 00:00:52,960 --> 00:00:55,760 Speaker 1: or the tumor may not be accessible at all. In 15 00:00:55,920 --> 00:01:00,000 Speaker 1: prostate cancer, the patient is often left incontinent and impotent. 16 00:01:00,040 --> 00:01:04,559 Speaker 1: In surgery is usually followed by chemotherapy to kill any 17 00:01:04,640 --> 00:01:09,399 Speaker 1: remaining cancer cells. Chemotherapy is a drug cocktail that is 18 00:01:09,520 --> 00:01:13,520 Speaker 1: in essence poison. The poison kills the cancer cells by 19 00:01:13,560 --> 00:01:17,440 Speaker 1: targeting cells that reproduce rapidly. The side effect is that 20 00:01:17,560 --> 00:01:20,520 Speaker 1: other cells in the body that happen to reproduce rapidly 21 00:01:20,880 --> 00:01:24,240 Speaker 1: like hair follicles, and the cells lining the stomach often 22 00:01:24,319 --> 00:01:28,000 Speaker 1: suffer as well. This explains the hair loss and nausea 23 00:01:28,360 --> 00:01:33,480 Speaker 1: that often accompanies chemotherapy. Another possibility is X ray therapy, 24 00:01:33,520 --> 00:01:36,680 Speaker 1: where multiple beams of X rays penetrate the body and 25 00:01:36,800 --> 00:01:40,360 Speaker 1: intersect at the tumor. The tumor receives a high enough 26 00:01:40,400 --> 00:01:43,800 Speaker 1: dose of X rays to damage the cancerous DNA and 27 00:01:43,959 --> 00:01:47,720 Speaker 1: kill the cancer cells, but there can be collateral damage 28 00:01:47,760 --> 00:01:50,360 Speaker 1: at the places where the X ray beams enter the 29 00:01:50,400 --> 00:01:54,280 Speaker 1: body and overshoot the tumor. Healthy tissue near a tumor 30 00:01:54,360 --> 00:01:58,520 Speaker 1: often gets damaged as well. There are other therapies, including 31 00:01:58,600 --> 00:02:02,920 Speaker 1: bits of radioactive serial commonly called seeds, embedded in and 32 00:02:02,960 --> 00:02:05,600 Speaker 1: around the tumor in the hope of killing the tumor 33 00:02:05,680 --> 00:02:10,639 Speaker 1: with nuclear radiation, various new and experimental drugs targeting things 34 00:02:10,720 --> 00:02:13,880 Speaker 1: like tumor blood supply, and so on. Most of the 35 00:02:13,919 --> 00:02:16,640 Speaker 1: techniques in use today have side effects that can be 36 00:02:16,760 --> 00:02:20,320 Speaker 1: quite unfortunate for the patient. This is why so many 37 00:02:20,400 --> 00:02:24,520 Speaker 1: people are getting excited about proton therapy. The idea here 38 00:02:24,639 --> 00:02:28,400 Speaker 1: is to use protons, which have been accelerated to near 39 00:02:28,560 --> 00:02:32,600 Speaker 1: light speed in a particle accelerator to kill cancer tumors. 40 00:02:33,120 --> 00:02:36,680 Speaker 1: The advantage of proton therapy is a good success rate 41 00:02:36,720 --> 00:02:40,120 Speaker 1: with a low incidence of side effects. So what is 42 00:02:40,160 --> 00:02:43,200 Speaker 1: a proton? If you think of a hydrogen atom, the 43 00:02:43,280 --> 00:02:46,440 Speaker 1: proton is the some atomic particle at the core of 44 00:02:46,440 --> 00:02:50,320 Speaker 1: the atom. A normal hydrogen atom has an electron orbiting 45 00:02:50,360 --> 00:02:54,240 Speaker 1: that proton. By stripping off the electron and leaving behind 46 00:02:54,280 --> 00:02:57,840 Speaker 1: a bare hydrogen nucleus, you have a proton that can 47 00:02:57,880 --> 00:03:01,880 Speaker 1: be used for proton therapy. Protons are so small that 48 00:03:01,960 --> 00:03:04,799 Speaker 1: they can fly through the body doing very little damage, 49 00:03:05,160 --> 00:03:07,280 Speaker 1: but they do slow down as they make their way 50 00:03:07,320 --> 00:03:11,440 Speaker 1: through tissue. Eventually, the protons come to a stop. Add 51 00:03:11,520 --> 00:03:15,120 Speaker 1: or near the stopping point, protons strip electrons off of 52 00:03:15,200 --> 00:03:19,560 Speaker 1: nearby atoms, changing important molecules in the process. If a 53 00:03:19,639 --> 00:03:23,640 Speaker 1: doctor delivers enough protons to a tumor, cells inside the 54 00:03:23,680 --> 00:03:28,560 Speaker 1: tumor die because of this electron activity. Some doctors described 55 00:03:28,600 --> 00:03:32,680 Speaker 1: protons as acting like a firecracker, avoiding damage to tissue 56 00:03:32,760 --> 00:03:36,920 Speaker 1: surrounding the tumor, but exploding inside the tumor. The reason 57 00:03:37,040 --> 00:03:40,160 Speaker 1: is that protons do damage when they come to rest, 58 00:03:40,800 --> 00:03:43,560 Speaker 1: So if they come to rest inside the tumor. The 59 00:03:43,640 --> 00:03:46,840 Speaker 1: tumor is the only thing to get significant damage from 60 00:03:46,880 --> 00:03:50,800 Speaker 1: the protons. The depth that the protons penetrate into the 61 00:03:50,840 --> 00:03:54,520 Speaker 1: body can be controlled by their speed. Compared to X 62 00:03:54,640 --> 00:03:58,000 Speaker 1: ray therapy, there is no exit dose that can harm 63 00:03:58,120 --> 00:04:01,320 Speaker 1: healthy tissue beyond the tumor, and there's only a very 64 00:04:01,360 --> 00:04:05,680 Speaker 1: small entry dose. The two big problems with proton therapy 65 00:04:05,800 --> 00:04:08,280 Speaker 1: right now are the fact that it is so new 66 00:04:08,640 --> 00:04:12,080 Speaker 1: and the cost. There are only a handful of proton 67 00:04:12,200 --> 00:04:15,240 Speaker 1: therapy facilities in the United States at the moment, and 68 00:04:15,320 --> 00:04:19,919 Speaker 1: these facilities are incredibly expensive, costing hundreds of millions of 69 00:04:19,960 --> 00:04:23,240 Speaker 1: dollars to build. The cost is coming from the need 70 00:04:23,360 --> 00:04:27,880 Speaker 1: for a complete, highly sophisticated particle accelerator at each facility. 71 00:04:28,320 --> 00:04:32,040 Speaker 1: The particle accelerator creates the protons and then accelerates them 72 00:04:32,080 --> 00:04:35,800 Speaker 1: to the precise speed needed to reach the tumor. Another 73 00:04:35,880 --> 00:04:39,640 Speaker 1: problem is the high number of visits. A typical prostate 74 00:04:39,720 --> 00:04:43,640 Speaker 1: cancer tumor might require forty daily visits to a proton 75 00:04:43,800 --> 00:04:47,880 Speaker 1: therapy facility over the course of two months, unless you 76 00:04:47,920 --> 00:04:50,760 Speaker 1: happen to live in the rare city that has a facility. 77 00:04:51,200 --> 00:04:54,760 Speaker 1: This means a long daily commute or a two month 78 00:04:54,800 --> 00:04:58,480 Speaker 1: hotel stay along with the cost of the forty sessions, 79 00:04:58,520 --> 00:05:01,440 Speaker 1: which can rise into the pends of thousands of dollars. 80 00:05:02,080 --> 00:05:05,720 Speaker 1: The hope is that technological advances will lower the cost 81 00:05:05,839 --> 00:05:09,680 Speaker 1: of new facilities, making the treatment much more accessible and 82 00:05:09,800 --> 00:05:13,679 Speaker 1: less expensive. If that happens, it could open a new 83 00:05:13,760 --> 00:05:19,000 Speaker 1: era in cancer treatment. 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