This blog is based on a suppositional paper written by Dr. James Watson, of DNA fame, and published in Open Biology. He argues that the presence of antioxidants in cancer cells blocks anticancer treatments. The only clinical evidence of which I am aware that supports his thesis is the study of Finnish male smokers which showed that those who took antioxidant supplements had a higher incidence of lung cancer, and there also are several studies of cancer cells in vitro that seem to demonstrate a similar effect of antioxidants.
Dr. Watson's paper is long and highly technical, so I will summarize the key points here and try to interpret them for the reader who is not heavily involved in cancer research. I might just begin by remarking that no interventional diet study involving the addition of antioxidants to the daily diet (beta carotene, Vitamin E, selenium, Vitamin A, and Vitamin C) has been shown to prolong the human life span. I will also touch on the possible reason for the benefit of aspirin in cancer prevention and why tests are now being done to see if the diabetes drug metformin has anti-cancer properties.
Most agents used to kill organ (non bone-marrow) cancers, including Xrays and chemotherapy, work by generating ROS, or reactive oxygen species (such as OH-) which block key steps in the cell cycle and thereby hasten apoptosis, or cell self-destruction. The presence of ROS also generates a hypoxic environment in the cell, which drives a conversion of the cell from an epithelial to a mesenchymal type. But at the same time, in self-protection, the presence of ROS causes the cell to generate antioxidants, which render the cell resistant if not immune to both ionizing radiation and chemotherapy. In addition, mesenchymal cells are more prone to travel and metastasize. So the presence of ROS is both an accelerator and a brake.
The presence of the Myc gene activator can drive cancer cells forward, as can the presence of inflammatory cytokines such as interleukin-6. It is therefore theorized than the cancer-preventing property of daily aspirin (most convincingly demonstrated in colon cancer) derives from its anti-inflammatory and cytokine suppressing effect. And it has been shown that the turning off of Myc drives cancer cells towards apoptosis.
Now in mouse models of cancer, the anti-diabetic drug metformin preferentially killed mesenchymal stem cells, which cells are the most resistant to chemotherapy and the most prone to metastasize. The reason for this is probably its blocking of oxidative phosphorylation. There are currently a number of ongoing studies where metformin is being added to standard anticancer chemotherapies in humans to look for an enhanced killing effect.
To summarize Dr. Watson's thesis, and again I refer the interested reader to his paper, anticancer chemotherapy and Xrays generate ROS. The presence of ROS has a two-fold effect: it drives the cancer cell towards apoptosis, or cell death, and at the same time it induces antioxidants which render the cell resistant to further anticancer treatment as well as inducing a transformation to a mesenchymal stem cell. It is not known if the antioxidants themselves drive this change in addition to inducing resistance to treatment.
Based on this theory, and the limited data to date, it would seem prudent to avoid adding antioxidants to your diet which in theory would increase the antioxidant levels in every cell in your body by diffusion. Remember the study of Vitamin E, touted as an oxidant, which showed (in two different studies) that an increase in the intake of Vitamin E increased the rate of cardiac events and heart attacks.
Showing posts with label Cancer. Show all posts
Showing posts with label Cancer. Show all posts
Monday, January 21, 2013
Friday, November 30, 2012
Do Statins Reduce Your Risk of Dying from Cancer?
There was a very interesting article published in the November 8, 2012 issue of the New England Journal of Medicine (vol. 367, pp 1792-1802) as well as an excellent analysis of the study published as an editorial comment in the same volume (pp 1848-1850). One theory about cancer growth is that those cells need cholesterol for cellular reproduction, so that any drug that lowers cholesterol should provide a benefit. The study was done in Denmark, which has a remarkably homogeneous population and moreover, because of national health care, has excellent registries of cancer diagnosis and incidence, as well as deaths from cancer, all cause mortality, and the prescribing of drugs. (The availability of such statistical data is one side benefit of national health care if the computer programs are written properly.)
The retrospective study reviewed data relating to medical care from 1995 to 2009, and encompassed almost 300,000 subjects. The hypothesis tested was that patients who were taking statins BEFORE the diagnosis of cancer would have a reduced cancer mortality. It was found that patients who were taking statins before the diagnosis of cancer had a reduction in their probability of dying from cancer from 100% to 85 % and the same reduction was found in mortality from any cause after the diagnosis of cancer. (The actual number of 85% +/- 2% is the hazard ratio, which is a statistical concept.) One remarkable fact was that the 15% reduction in mortality risk was independent of the dose of the statin(!).
Several clinical events and facts were not controlled for. No mention is made of cigarette smoking in the two groups, or if they had had cancer surgery. Also, no mention was made of OTC aspirin or NSAID use, and we know of several studies linking such use to a reduced incidence of colon cancer.
It is naturally suggested that a clinical study be made to test the hypothesis that was generated by this retrospective study, i.e. the hypothesis that statin use has a positive effect on cancer mortality as well as on all-cause mortality. I want to re-emphasize that this was a statistical analysis, and not a forward double-blind study so it would be tempting but scientifically incorrect to draw a clinical conclusion from the results. The problem I foresee is that no one will want to be in the placebo arm of the study, and risk not lowering his/her chance of dying. (This is in fact what happened when St. Vincent's Hospital in NYC tried to test drugs for AIDS with a placebo arm in the study. The political pressure was so great that the FDA granted the researchers permission to omit the placebo arm.) I predict that once the news of this study gets out to the general public, then millions of people will start taking statins of their own accord (probably from Mexico since almost every drug that is a prescription-only drug in the U.S. is sold OTC in Mexico).
Isn't the motto of Dupont, the giant chemical company, "Better living through chemistry"?
The retrospective study reviewed data relating to medical care from 1995 to 2009, and encompassed almost 300,000 subjects. The hypothesis tested was that patients who were taking statins BEFORE the diagnosis of cancer would have a reduced cancer mortality. It was found that patients who were taking statins before the diagnosis of cancer had a reduction in their probability of dying from cancer from 100% to 85 % and the same reduction was found in mortality from any cause after the diagnosis of cancer. (The actual number of 85% +/- 2% is the hazard ratio, which is a statistical concept.) One remarkable fact was that the 15% reduction in mortality risk was independent of the dose of the statin(!).
Several clinical events and facts were not controlled for. No mention is made of cigarette smoking in the two groups, or if they had had cancer surgery. Also, no mention was made of OTC aspirin or NSAID use, and we know of several studies linking such use to a reduced incidence of colon cancer.
It is naturally suggested that a clinical study be made to test the hypothesis that was generated by this retrospective study, i.e. the hypothesis that statin use has a positive effect on cancer mortality as well as on all-cause mortality. I want to re-emphasize that this was a statistical analysis, and not a forward double-blind study so it would be tempting but scientifically incorrect to draw a clinical conclusion from the results. The problem I foresee is that no one will want to be in the placebo arm of the study, and risk not lowering his/her chance of dying. (This is in fact what happened when St. Vincent's Hospital in NYC tried to test drugs for AIDS with a placebo arm in the study. The political pressure was so great that the FDA granted the researchers permission to omit the placebo arm.) I predict that once the news of this study gets out to the general public, then millions of people will start taking statins of their own accord (probably from Mexico since almost every drug that is a prescription-only drug in the U.S. is sold OTC in Mexico).
Isn't the motto of Dupont, the giant chemical company, "Better living through chemistry"?
Sunday, August 5, 2012
Do Xrays and Cosmic Rays Cause Cancer?
I will review this topic wearing both my hats as a former physics professor (who also did research on the effect of ionizing radiation on tissue) and a former medical professor. I am not here going to criticize the statistical methods used to draw conclusions (e.g. in "Projected Cancer Risks From CT Scans..." Arch. Int. Med. Vol 169, pp 2071-2077, 2009.) Rather I will discuss the medical evidence for the carcinogenic effects of radiation and see if there is any valid scientific evidence that enables us to extrapolate these results downward so as to predict the possibly carcinogenic effect of the Xrays we are exposed to by CT scans and cosmic rays. I understand that this is a "hot" topic (no pun intended), and as usual in such cases, the heat of an issue tends to be in inverse proportion to the light that experimental facts shed on the issue. As Voltaire famously mentioned, no one is burned at the state because people disagree with the statement that 7 x 8 = 56, although Giordano Bruno was burned at the stake for maintaining that the earth was not the center of the universe.
I am going to restrict my discussion to adults. The different units of radiation measure will also not concern us directly, because we have no way of accurately determining how much of a given wavelength of Xradiation a body organ will absorb, let alone the DNA damage it will cause. All the hard data we have really comes from the development of cancers in the survivors of the two atomic bombs dropped on Japan, and we begin by assuming that the response of Caucasian and black tissue to radiation is the same as the response of Japanese tissue, insofar as its carcinogenicity is concerned, an assumption that is, thank God, not borne out by any accidents of nature or man. (Chernobyl is a special case, since the doses there were not comparable to those of diagnostic radiation, and a lot of the radiation damage and cancer were caused by ingestion of radioactive isotopes.)
The question to which there has been no clinical answer is whether or not the risk from the radiation released by an atomic bomb can be extrapolated down in a linear fashion to medical Xrays or our daily bombardment by cosmic rays. Is there a threshold, a level of radiation below which Xrays will not induce cancer in humans? Is the only "safe" dose (i.e. non cancer-causing) of Xrays no Xrays? This question has never been answered by any clinical study, and all the assumptions and estimations of the dangers of diagnostic Xrays are based upon the unproven assumption that there is no such threshold, and that even one photon in the Xray energy range can cause cancer in a human cell.This assumption completely ignores the reparative capabilities of DNA. We also have never answered the question of whether or not the risk from successive Xrays is cumulative, so that we can add the putative carcinogenic risk of one Xray to the next one. Somehow this is counterintuitive, unless we are saying that 10 mammograms in 10 days are no more dangerous than 10 mammograms each spaced a year after the previous one. This would seem to say that there is no DNA repair process for Xray damage, even though man lives his whole life exposed to very high energy cosmic rays.
I would argue that there must be a threshold dose below which Xrays do not cause cancer, and therefore linear extrapolation downward from the cancer incidence in A-bomb survivors is invalid. We know that we are constantly bombarded by cosmic Xrays which have energies thousands of times higher than you are exposed to by an Xray machine. Note that I said energy, not intensity. (Intensity is measured in photons per square centimeter per second.) We are partially shielded from cosmic radiation by the ozone layer and by the earth's atmosphere. People living in Denver are a mile higher than denizens of New York City, and therefore have one mile less of atmospheric shielding. Nevertheless, the cancer rate in Denver is identical to that in the lowlands. Therefore the increased cosmic Xradiation that Denverians receive is not enough to measurably affect their cancer rate. It therefore follows that there is a threshold, and that we have no idea of what a safe dose of radiation is, except that "too much" can damage tissues directly by overheating and frying them.
I can also adduce evidence that the cell damage from Xrays is cumulative. It is well known that as you get older, the incidence of cancer increases. But as you get older, you have been exposed to more and more cosmic Xrays originating from deep in the universe. Is it possible that cosmic Xrays are the main cause of the increase in cancer with aging, in part by damaging the nuclei of cells in our body and in part by damaging our immune system? For that matter, we know that the coronary arteries under the left breast have in increased rate of calcification if the breast is radiated for breast cancer. Could the exposure of all our arteries to the continuous rain of cosmic Xrays also be the explanation for the increased hardening of the arteries with age? Could this also explain the loss of brain cells with aging, and possibly contribute to Alzheimer's disease in that amyloid plaques are the body's attempt to heal radiation damage to the brain by creating scar tissue?
There has been no satisfactory explanation of why our cancer incidence increases with age, except to note that our immune system also weakens with age. But correlation is not causation, and, as I suggested above, we are then left with the question of why the immune system weakens with age. Since we know that radiation can damage the human immune system, then the continuous cosmic radiation is as good an explanation as any. It may even explain why few if any humans live beyond 120 years: the shortening of telomeres with age may also be a consequence of cosmic radiation bombardment, and we can never test this hypothesis because the energy of cosmic radiation is thousands of times higher than xrays we generate here on earth.
In summary, there is no clinical evidence one way or another that our estimates of a "safe" dose of radiation are correct, and we have no way of determining the life-long effect on us of our bombardment by ultra high energy cosmic Xrays.
I am going to restrict my discussion to adults. The different units of radiation measure will also not concern us directly, because we have no way of accurately determining how much of a given wavelength of Xradiation a body organ will absorb, let alone the DNA damage it will cause. All the hard data we have really comes from the development of cancers in the survivors of the two atomic bombs dropped on Japan, and we begin by assuming that the response of Caucasian and black tissue to radiation is the same as the response of Japanese tissue, insofar as its carcinogenicity is concerned, an assumption that is, thank God, not borne out by any accidents of nature or man. (Chernobyl is a special case, since the doses there were not comparable to those of diagnostic radiation, and a lot of the radiation damage and cancer were caused by ingestion of radioactive isotopes.)
The question to which there has been no clinical answer is whether or not the risk from the radiation released by an atomic bomb can be extrapolated down in a linear fashion to medical Xrays or our daily bombardment by cosmic rays. Is there a threshold, a level of radiation below which Xrays will not induce cancer in humans? Is the only "safe" dose (i.e. non cancer-causing) of Xrays no Xrays? This question has never been answered by any clinical study, and all the assumptions and estimations of the dangers of diagnostic Xrays are based upon the unproven assumption that there is no such threshold, and that even one photon in the Xray energy range can cause cancer in a human cell.This assumption completely ignores the reparative capabilities of DNA. We also have never answered the question of whether or not the risk from successive Xrays is cumulative, so that we can add the putative carcinogenic risk of one Xray to the next one. Somehow this is counterintuitive, unless we are saying that 10 mammograms in 10 days are no more dangerous than 10 mammograms each spaced a year after the previous one. This would seem to say that there is no DNA repair process for Xray damage, even though man lives his whole life exposed to very high energy cosmic rays.
I would argue that there must be a threshold dose below which Xrays do not cause cancer, and therefore linear extrapolation downward from the cancer incidence in A-bomb survivors is invalid. We know that we are constantly bombarded by cosmic Xrays which have energies thousands of times higher than you are exposed to by an Xray machine. Note that I said energy, not intensity. (Intensity is measured in photons per square centimeter per second.) We are partially shielded from cosmic radiation by the ozone layer and by the earth's atmosphere. People living in Denver are a mile higher than denizens of New York City, and therefore have one mile less of atmospheric shielding. Nevertheless, the cancer rate in Denver is identical to that in the lowlands. Therefore the increased cosmic Xradiation that Denverians receive is not enough to measurably affect their cancer rate. It therefore follows that there is a threshold, and that we have no idea of what a safe dose of radiation is, except that "too much" can damage tissues directly by overheating and frying them.
I can also adduce evidence that the cell damage from Xrays is cumulative. It is well known that as you get older, the incidence of cancer increases. But as you get older, you have been exposed to more and more cosmic Xrays originating from deep in the universe. Is it possible that cosmic Xrays are the main cause of the increase in cancer with aging, in part by damaging the nuclei of cells in our body and in part by damaging our immune system? For that matter, we know that the coronary arteries under the left breast have in increased rate of calcification if the breast is radiated for breast cancer. Could the exposure of all our arteries to the continuous rain of cosmic Xrays also be the explanation for the increased hardening of the arteries with age? Could this also explain the loss of brain cells with aging, and possibly contribute to Alzheimer's disease in that amyloid plaques are the body's attempt to heal radiation damage to the brain by creating scar tissue?
There has been no satisfactory explanation of why our cancer incidence increases with age, except to note that our immune system also weakens with age. But correlation is not causation, and, as I suggested above, we are then left with the question of why the immune system weakens with age. Since we know that radiation can damage the human immune system, then the continuous cosmic radiation is as good an explanation as any. It may even explain why few if any humans live beyond 120 years: the shortening of telomeres with age may also be a consequence of cosmic radiation bombardment, and we can never test this hypothesis because the energy of cosmic radiation is thousands of times higher than xrays we generate here on earth.
In summary, there is no clinical evidence one way or another that our estimates of a "safe" dose of radiation are correct, and we have no way of determining the life-long effect on us of our bombardment by ultra high energy cosmic Xrays.
Saturday, February 25, 2012
Cancer Part I
This blog is not a general review of cancers, but rather simple facts about all cancers in general. I was motivated to write this blog as a result of my volunteer work with Gilda's Club of Northern New Jersey. It really is true that only a person who has cancer can really understand and relate to another person who has or had cancer. There still are a lot of untrue beliefs floating around, and this blog is an attempt to correct some of them.
First, the only trustworthy site is WWW.NATIONAL CANCER INSTITUTE.GOV. This is the only totally unbiased reference available on the internet. It lists all the cancers by organ, and then breaks the organ cancer down into subtypes (e.g. nodal non-Hodgkins lymphoma). It lists the standard treatment, secondary treatments, etc. and also refers to a site where you can find a list of clinical trials. Any website published by a hospital or any other institution is biased by institutional philosophy----e.g. the chairman of the Urology Dept. at John Hopkins published a book about the virtues of using surgery to treat prostate cancer, so if they have a patients' website, you might see some bias. But the NCI has no such axe to grind.
Second, all doctors want to heal their patients. There are really NO SECRETS in medicine. In these days of Oprah, etc., if a doctor had a new cure for cancer, he/she would scream it from the rooftops, get on Oprah and Jay Leno, be on talk shows, etc. We all want to cure all our patients, and we are constantly seeking new treatments via journal article, conferences, etc. (And The National Enquirer is not now and never will be a refereed medical journal.)
Each major hospital has a weekly conference open to all its oncologists and other interested physicians. In a large city, there are monthly cancer conferences to which all hospitals send a doctor-delegate. Finally there are quarterly divisional meetings as well as annual conferences on cancer to which all doctors are invited. We also have publications by the Mayo Clinic, etc., which are distributed to all interested doctors. So again, there are no secrets about treating cancer. If a doctor had a new method, he/she would publicize it so as to become famous as well as rich.
The only people who really can judge a physician's brains and abilities are the residents who work with him/her especially if they have operated with the surgeon in question. No one else, including your next door neighbor, your best friend, and your aunt Sally know anything about the doctor in question. When I was a medical resident at Columbia , I asked all the surgical residents who the best general surgeons, breast surgeons, vascular surgeons, gynecologists, oncologists, chest surgeons, heart surgeons, orthopedic surgeons, neuro surgeons, urological surgeons, etc. were, and I referred my patients only to those surgeons. In fact, I convinced my older partner to switch away from the surgeon to whom he usually referred his patients.
The most certain method of treating/eliminating cancer is to surgically remove the mass before it has metastacized. This means taking out the tumor en bloc, with a good margin (i.e. non-cancerous tissue) around it. The surgeon will generally also remove or sample nearby lymph notes to look for local spread. This is why it is so difficult to treat brain, pancreatic, or ovarian cancer. Note: I said difficult, not impossible. As a rule, it is difficult to get a good margin around a brain tumor because the tumor has spread its tentacles (like a "crab" aka "cancer" in stellar constellations) into vital tissues that control memory or the contraction of muscles.And unlike most organs, neither the ovary nor the pancreas is surrounded by a protective sheath, as is the colon, or the liver, so these two cancers spread locally very easily, although as a rule they are detected while they are still contained within the abdominal cavity.
Surgery is often followed by radiation therapy and/or chemotherapy. The idea is to get any few cells that have escaped (micro-metastases) beyond the organ before the surgery. Of course with any cancer based in the bone marrow such as the leukemias, the lymphomas and the myelomas, surgery is usually of no use. All these treatments rest on the same principles: cancer cells have a higher metabolic rate and multiply faster than nearby normal cells in the same organ. We have known for almost 100 years that cancer cells have a higher metabolic rate; this was determined by showing that they utilize oxygen at a higher rate that normal cells. This is also the basis for the PET scan, which replaces oxygen-16 with radioactive oxygen-17 in a sugar molecule, and determining which cells absorb and use this sugar the fastest.
All radiation and chemotherapy modes (with a few exceptions, such as we have with l-asparaginase in one type of leukemia, or the use of monoclomal antibodies to kill other cancers) can kill all cells, and our hope is that the more rapidly dividing cancer cells will be killed faster than normal tissue. This is why treatment schedules are carefully monitored as to dosage (mg/kg), time, and frequency. You want the normal tissue to be able to recover between treatments.
I have barely scratched the surface of this topic, and have deliberately omitted discussion of the role of your immune system in controlling or killing cancer and cancer cells, because then the blog would have been much too long.
First, the only trustworthy site is WWW.NATIONAL CANCER INSTITUTE.GOV. This is the only totally unbiased reference available on the internet. It lists all the cancers by organ, and then breaks the organ cancer down into subtypes (e.g. nodal non-Hodgkins lymphoma). It lists the standard treatment, secondary treatments, etc. and also refers to a site where you can find a list of clinical trials. Any website published by a hospital or any other institution is biased by institutional philosophy----e.g. the chairman of the Urology Dept. at John Hopkins published a book about the virtues of using surgery to treat prostate cancer, so if they have a patients' website, you might see some bias. But the NCI has no such axe to grind.
Second, all doctors want to heal their patients. There are really NO SECRETS in medicine. In these days of Oprah, etc., if a doctor had a new cure for cancer, he/she would scream it from the rooftops, get on Oprah and Jay Leno, be on talk shows, etc. We all want to cure all our patients, and we are constantly seeking new treatments via journal article, conferences, etc. (And The National Enquirer is not now and never will be a refereed medical journal.)
Each major hospital has a weekly conference open to all its oncologists and other interested physicians. In a large city, there are monthly cancer conferences to which all hospitals send a doctor-delegate. Finally there are quarterly divisional meetings as well as annual conferences on cancer to which all doctors are invited. We also have publications by the Mayo Clinic, etc., which are distributed to all interested doctors. So again, there are no secrets about treating cancer. If a doctor had a new method, he/she would publicize it so as to become famous as well as rich.
The only people who really can judge a physician's brains and abilities are the residents who work with him/her especially if they have operated with the surgeon in question. No one else, including your next door neighbor, your best friend, and your aunt Sally know anything about the doctor in question. When I was a medical resident at Columbia , I asked all the surgical residents who the best general surgeons, breast surgeons, vascular surgeons, gynecologists, oncologists, chest surgeons, heart surgeons, orthopedic surgeons, neuro surgeons, urological surgeons, etc. were, and I referred my patients only to those surgeons. In fact, I convinced my older partner to switch away from the surgeon to whom he usually referred his patients.
The most certain method of treating/eliminating cancer is to surgically remove the mass before it has metastacized. This means taking out the tumor en bloc, with a good margin (i.e. non-cancerous tissue) around it. The surgeon will generally also remove or sample nearby lymph notes to look for local spread. This is why it is so difficult to treat brain, pancreatic, or ovarian cancer. Note: I said difficult, not impossible. As a rule, it is difficult to get a good margin around a brain tumor because the tumor has spread its tentacles (like a "crab" aka "cancer" in stellar constellations) into vital tissues that control memory or the contraction of muscles.And unlike most organs, neither the ovary nor the pancreas is surrounded by a protective sheath, as is the colon, or the liver, so these two cancers spread locally very easily, although as a rule they are detected while they are still contained within the abdominal cavity.
Surgery is often followed by radiation therapy and/or chemotherapy. The idea is to get any few cells that have escaped (micro-metastases) beyond the organ before the surgery. Of course with any cancer based in the bone marrow such as the leukemias, the lymphomas and the myelomas, surgery is usually of no use. All these treatments rest on the same principles: cancer cells have a higher metabolic rate and multiply faster than nearby normal cells in the same organ. We have known for almost 100 years that cancer cells have a higher metabolic rate; this was determined by showing that they utilize oxygen at a higher rate that normal cells. This is also the basis for the PET scan, which replaces oxygen-16 with radioactive oxygen-17 in a sugar molecule, and determining which cells absorb and use this sugar the fastest.
All radiation and chemotherapy modes (with a few exceptions, such as we have with l-asparaginase in one type of leukemia, or the use of monoclomal antibodies to kill other cancers) can kill all cells, and our hope is that the more rapidly dividing cancer cells will be killed faster than normal tissue. This is why treatment schedules are carefully monitored as to dosage (mg/kg), time, and frequency. You want the normal tissue to be able to recover between treatments.
I have barely scratched the surface of this topic, and have deliberately omitted discussion of the role of your immune system in controlling or killing cancer and cancer cells, because then the blog would have been much too long.
Saturday, September 5, 2009
Radiation, X-rays, Medicine, and Cancer
The question of the relationship between radiation, X-rays, cosmic rays, (radioactive) radon gas, and cancer is a murky one, and there are many unanswered questions. In some cases, exposure to radiation gives the patient an increased lifetime risk for cancer, and for reasons unknown to medical science, the risk for women is greater than the risk for men. Because of the very long time delays that can be involved (up to 45 years has been recorded), it would appear that radiation is a cancer potentiator, rather than a direct inducer.(But radiation itself can be an inducer for a cell that has already been potentiated.) In the cases (Hiroshima, Chernobyl) where a direct and short time correlation has been observed, it is probable that the intensity of the radiation is also important. We know that high energy, high intensity radiation is lethal to humans, and lower intensity radiation is lethal to cancer cells. We also know about radiation sickness. We have a rough idea of the lethal dose of radiation (which is different for alpha rays, beta rays, photons (gamma rays), neutrons, and cosmic radiation). We know how much radiation shielding astronauts need to keep them alive.
We do not know, and will never know, the LD50 dose for humans for any type of radiation. We cannot even measure human radiation exposure. The unit called the Sievert is used, but the Sievert depends on the type of radiation, the energy, and, most important of all, the amount of radiation energy absorbed by various tissues, and this latter term can only be estimated (and very poorly, at that) from animal studies. We also know that we are missing some scientific factor: The residents of Denver dwell 5,000 feet higher than the residents of NYC, and therefore have one mile less of atmospheric shielding from cosmic rays. How is it then that Denver residents do not have a significantly higher rate of cancer than do Manhattanites?
There was a recent article published in JAMA detailing the increased amount of radiation we are all getting over our lifetime from X-ray studies. In fact, the U.S. gov't has officially classified radiation as a carcinogen. Why is it then that no patient is ever given a release form to sign than delineates the estimated immediate and lifetime personal carcinogenic risk from the proposed X-ray study? (I once tried to generate and have my ER patients sign such a form, and I was immediately told by the chairmen of Radiology and Medicine to stop.)
Thirty years ago, when I was a physics professor, I started to do some experiments with a colleague of mine from Princeton. Since he had a joint appointment with Princeton Physics Dept. and the Princeton Plasma Physics Lab, which meant that he also worked on the Stellarator, our research was classified (and still is, for all I know). We then co-opted a physicist at Oak Ridge Nat'l Labs for good radioactive sources. We were trying to see if there is a minimum radiation dose below which there is NO cancer risk. The belief now as well as then was that there is not, and that there is no minimum safe dose of radiation. We were unable to come to a definite conclusion. We could not determine whether or not a certain straight line on a graph passed through the origin.
The universal fear of radiation is so great that MRI was initially called by its correct name NMR (Nuclear Magnetic Resonance), but NMR was changed to MRI so as to not scare patients away from the MRI. We could greatly decrease food poisoning and contamination with germs and bugs by subjecting wheat, fruit, etc., to killing levels of radiation, but again, the public is so fearful of the possible consequences of radiation that Congress has never passed a food-radiation enabling law, and we can therefore expect future lethal food outbreaks similar to the E. Coli in hamburgers. The one time we should have been fearful, we were not, and many women who licked camel's hair brushes to make a finer point before painting the numbers on a wristwatch with a radioactive chemical developed mouth and jaw cancers.
I guess this blog is written with mixed emotions, and no firm purpose. As a physicist I have the greatest respect for the dangers of radiation, and as a physician, I know its many beneficial uses. I wish we all knew more!
We do not know, and will never know, the LD50 dose for humans for any type of radiation. We cannot even measure human radiation exposure. The unit called the Sievert is used, but the Sievert depends on the type of radiation, the energy, and, most important of all, the amount of radiation energy absorbed by various tissues, and this latter term can only be estimated (and very poorly, at that) from animal studies. We also know that we are missing some scientific factor: The residents of Denver dwell 5,000 feet higher than the residents of NYC, and therefore have one mile less of atmospheric shielding from cosmic rays. How is it then that Denver residents do not have a significantly higher rate of cancer than do Manhattanites?
There was a recent article published in JAMA detailing the increased amount of radiation we are all getting over our lifetime from X-ray studies. In fact, the U.S. gov't has officially classified radiation as a carcinogen. Why is it then that no patient is ever given a release form to sign than delineates the estimated immediate and lifetime personal carcinogenic risk from the proposed X-ray study? (I once tried to generate and have my ER patients sign such a form, and I was immediately told by the chairmen of Radiology and Medicine to stop.)
Thirty years ago, when I was a physics professor, I started to do some experiments with a colleague of mine from Princeton. Since he had a joint appointment with Princeton Physics Dept. and the Princeton Plasma Physics Lab, which meant that he also worked on the Stellarator, our research was classified (and still is, for all I know). We then co-opted a physicist at Oak Ridge Nat'l Labs for good radioactive sources. We were trying to see if there is a minimum radiation dose below which there is NO cancer risk. The belief now as well as then was that there is not, and that there is no minimum safe dose of radiation. We were unable to come to a definite conclusion. We could not determine whether or not a certain straight line on a graph passed through the origin.
The universal fear of radiation is so great that MRI was initially called by its correct name NMR (Nuclear Magnetic Resonance), but NMR was changed to MRI so as to not scare patients away from the MRI. We could greatly decrease food poisoning and contamination with germs and bugs by subjecting wheat, fruit, etc., to killing levels of radiation, but again, the public is so fearful of the possible consequences of radiation that Congress has never passed a food-radiation enabling law, and we can therefore expect future lethal food outbreaks similar to the E. Coli in hamburgers. The one time we should have been fearful, we were not, and many women who licked camel's hair brushes to make a finer point before painting the numbers on a wristwatch with a radioactive chemical developed mouth and jaw cancers.
I guess this blog is written with mixed emotions, and no firm purpose. As a physicist I have the greatest respect for the dangers of radiation, and as a physician, I know its many beneficial uses. I wish we all knew more!
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