Hello Claudia, thank you for sharing your testimony. I'm glad the Lord was merciful in his dealings with you. Cancer is an awful thing.
What I have learned from my class as far as cancer statistics and radiation. These are straight out of my in class notes:
Cancer currently claims 1 million lives each year in America.
Its the #2 killer of Americans behind cardiovascular disease.
Cancer is a disease of old age. People are living longer now and so we are getting the diseases of older age.
Environmental risk factor: RadiationSolar radiation (UV)Creates thiamine dimers
This causes DNA to buckle which results in errors in replication
700,000 non-melanoma skin cancers a year and the number is going up
Approximately 2 million cases world way
Largely curable, mostly basal and squamous cell carcinomas
One can be exposed to various wave-lengths of UV which determines whether its UV A, B or C
A is long wave length and used in tanning salons
B is short wave length, less than 350 nm
The most serious skin cancer is melanoma
35,000 deaths a year
132,000 deaths worldwide
One of the genes rendered nonfunctional by UV exposure is the p53 gene
P53 is involved in more cancer than any other gene
Ionizing radiationComes in several forms
X-raysAt the turn of the last century, in the 1900’s, workers that worked with x-rays developed a disproportionate amount of leukemia's
3 to 4 times the general population
It has been estimated that one cancer will develop for about every 1-million x-rays
That's 300-400 people a year
Do a risk-benefit analysis in deciding whether to get an x-ray or not
CAT Scans have 30 times more radiation than x-rays
X-rays that are used to treat cancer are used at very high doses and as a consequence of that the chance of causing secondary tumors is much greater
Decay of radioactive compoundsWe have seen this in the survivors of the bombings of Hiroshima and Nagasaki
Many of the survivors developed various kinds of cancer
There are two measure when we evaluate the carcinogenic potential of radiationThe ability of radiation to penetrate tissueRAD (radiation equivalent mean)
This is the amount absorbed by tissue
How much damage is it going to do to the tissue that it just penetratedREM (radiation equivalent in man)
This is basically RADs corrected for the biological effectiveness of the particular form of radiation in doing damage
Example: alpha particles which are emitted by radioactive elements are far more damaging than x-rays
About 20 times more damaging
1 RAD of x-ray exposure is equal to 1 REM
1 RAD of alpha particle exposure is equal to 20 REM
The annual dose of UV exposure is between 0.3-0.4 REMS
80% of this comes from just being alive
The other 20% comes from medicinal sources
Last year we had between 300-400 million x-rays given
Risk factor: VirusesThere are viruses that will transform normal cells into a tumor cell
We refer to these viruses as:
Oncogenic viruses, tumor viruses or transforming viruses
Viruses are causative agents from an epidemiologic perspective of certain human cancers
On a world wide bases viruses cause 15-20% of all cancer
Everything we know about cancer we have learned from studying and understanding viruses and their role in cancer
Hepatitis B Virus (HBV)A major risk factor for hepatocellular carcinoma
Responsible for a significant amount of world wide cancers
Virus attacks hepatocytes
This tell us that the hepatocytes have a receptor for the virus
The virus can cause acute liver damage
5-10% of individuals that are infected by this virus will not have the viral infection resolved
From the population, these are the chronic virus carries and will show greater incidence of liver cancer
Epidemiological studies have shown that about 10% of adults in the USA get infected by HBV. Of that, less than 1%will be chronic carries of the virus
In China 100% of adults have been exposed to HBV and 10-15% will be chronic carriers
This shows that the virus is associated with the cancer
Experimentally you can inject HBV into mice and see if they develop cancer
You can also inject HBV into cells in tissue culture and see if they develop cancer
You can also isolate cells from a patient operated on for hepatocellular carcinoma and see if the virus is part of it
There is a several year lag time. Populations in Asia are exposed during childhood and don't develop the cancer until their 30’s-40’s
About 23 years ago a vaccine was developed for HBV
There are other carcinogens that will exacerbate this chronic infection and that includes:
Alcohol
Contributes to cirrhosis of the liver
Aflatoxin
Potent mutagen for liver cells
Human papillomavirus (HPV)A risk factor that can cause malignant and benign neoplasms
Cervical and other anogenital carcinomas
Cervical cancer occurs less frequently in nuns
Cervical cancer occurs more frequently in women who have had multiple sex partners
Cervical cancer occurs more frequently in women who are married to men whose first wife had cervical carcinomas
All these events suggest a venereal transmitted disease
Squamous cell skin carcinomas
In 1983 a distinct papillomavirus was isolated from a cervical carcinoma sample
HPV16 was found to be involved in 50% of all cervical cancers
HPV18 was found to be involved in another 20%
HPV33 was found to be involved in another 10%
Today we know that 90-99% of all cervical cancers are virally caused by HPV
There are other strains of HPV that will cause genital infections but they are not transforming viruses
Like HBV there is a long lag period that could be several decade
Today there is a vaccine, Gardasil, that can be used for HBV
Epstein-Barr virus (EPV)First virus that was implicated in cancer
Associated with Burkitt’s and other B-cell lymphomas
Burkitt’s lymphoma is a lymphoma of childhood prevalent in parts of Africa
Associated with nasopharyngeal carcinoma in parts of China
Very rare to see Epstein-Barr virus to be implicated in cancer in other places
There is a geographic restriction
90% of people around the world are infected with EPV
They either have no symptoms or they have infectious mononucleosis
Individuals who have mononucleosis, the cell that is infected is the B-lymphocyte
Cell will have limited proliferation but it will not be transformed
Prevalent to the area where Burkitt’s lymphoma runs rampant in Africa is also Malaria
Parasites don't want you dead, they want to derive to nutrients from you
It depressed our immune system which may lead EPV to have a far greater affect on them then other people around the world
Human immunodeficiency virus (HIV)Cancers caused:
Lymphomas
Kaposi’s sarcoma
Angogenital carcinomas
Risk factor: Heredity The vast majority of patients with cancer have no inherited their disease
They will not pass their disease on to children
However, even though cancer is not considered a inherited disease, there are incidences that increases to susceptibility of the disease that can now be passed onto the offspring
That includes some rare forms of cancer as well as genetic diseases
That includes some rare forms of cancer as well as genetic diseases
Figure: Examples of inherited cancersAs we’ve seen before FAP is an inherited genetic condition that leads to the formation of lots of benign tumors and a small population of individuals who have that can lead to colon cancer
Wilms’ tumor has an inherited susceptibility as well as retinoblastoma
There are also diseases of genetic instability and diseases of immunodeficiency’s and individuals with those diseases show an increase in development in certain types of cancers
What you cant see in the illustration is that the gene that was inherited, it was always a defective tumor suppressor gene
If we have these rare susceptibilities it is going to be because of defective tumor suppressor genes
Figure: Mode of inheritanceThe mode of inheritance suggest that the susceptibility is determined by single genes and that they are transmitted in a genetically dominate fashion
Large C that dad has the actual cancer gene
In this case, half of the offspring’s will inherit the susceptibility gene
The gene functions in a dominate fashion
Even in the presence of another normal gene, these individuals will almost certainly develop the cancer
These inherited cancers represent a group that have a “direct-effect” on the cells that will ultimately become the neoplastic cells
This has to be contrasted with certain other disorders such as those of genetic instability or inherited immunodeficiency where the effect is going to be an indirect one
The effect is not going to be on a cell that is going to be the cancer cell but it will be on a cell that maybe involved with preventing the onset of disease
An example of a “direct-effect”:
RetinoblastomaThe inherited gene is ultimately going to manifest its activity in retinal cells
These individuals will have an increased predisposition of developing that disorder
An example of a “indirect-effect”:
A consequence of not dominant genes but recessive genes
In order for the disorder ot be manifested, both parents must carry the gene
This is why its far rare
Xeroderma pigmentosum is a condition of genetic instability.
It doesn't allow DNA to be repaired effectively
Particularly DNA that has been damaged by UV exposure
The defect is in a gene that encodes a DNA repair enzyme called UV-specific endonuclease
Rare condition-occurs in 1 out of 250 million children born
Inherited immunodeficiency known as Ataxia telangiectasia This is an inherited immunodeficiency
Just like acquired immunodeficiency like AIDs, just like patients that are on immunosuppressive drugs, individuals with ataxia telangiectasia are much more susceptible to the development of cancer
If the immune system is not functioning properly then the chances of developing tumors particularly tumors lymphocytes and other immune cells increases
We see in patients with ataxia telangiectasia an increase in lymphomas and in some cases leukemia’s
There maybe a viral connection
Environmental risk factor: Occupation risk factorsBoys who cleaned chimney soot and developed scrotal carcinomas
Asbestos workers got cancer as well as their wife’s who washed their laundry
Got a rare form of lung cancer called mesothelioma
Occupation carcinogens account for about 5% of cancers
Our concerns are that today we are using new chemicals and we don't know the affect they will have on us until 20 years
Environmental risk factor: HormonesBack in the 1940’s, a lot of pregnant women were given synthetic estrogen known as DES.
In the 1970’s their daughters were found to have been developing vaginal and cervical cancer after the 10-20 year lag period
This was the first evidence that estrogen can be problematic
Women still do take extra estrogen
Important effect in ameliorating the ravages of menopause
Beneficial and preventing the development of osteoporosis
Our evidence is not complete
For a period of time women were told that if they took progesterone along with estrogen it will prevent the adverse effect of estrogen
Large studies then came along and showed it not to be true
Other studies came to show that it may not be so clear
Most evidence suggest that extra estrogen is not a good thing to have because it's a promoting agent for breath and cervical epithelial cells
Environmental risk factor: DietThere are study’s that suggest that dietary components can be responsible for anywhere up to 30% or so of the cancers we see
Figure: Dietary factors and cancer risk
The problem with this illustration is that the studies that have been done are not nearly as incontrovertible as were those that have shown tobacco smoke and radiation to be major carcinogens
A lot of the studies that have shown some of these dietary components have either been controversial or in some cases contradictory
High FatIncreased risk of colorectal and possibly breast carcinomas
Figure: Breast cancer death rates vs dietary fat intake
As you consume more dietary fat the incidence of breast cancer goes up
The greatest consumers consists of the USA, Canada, Great Britain
The lowest consumers consists of Thailand and some Asian countries
There’s a problem with this illustration, its that there can be many other differences within a country besides just their consumption of dietary fatStudies showed that rats on a high fat diet and high rates of mammary tumor
Its not always like this when you go out into the general population
Even studies that have not been able to show conclusively show the association between dietary fat and breast cancer have shown a correlation between dietary fat and colorectal carcinomas
There is a 2-fold increase in the risk of colorectal carcinoma in individuals that consume around 44% of their daily diet in fat as compared to those who consume under 30%
The risk for endometrial carcinoma is 2-5 times greater for women who weight more than 165 pounds as compared to women who weight less than 125 pounds
The basis for this association is on the fact that fat cells produce estrogen
Now you have multiple sources of estrogen
Estrogen drives the proliferation of endometrial epithelium cells
Increased proliferation beyond the norm will lead to endometrial carcinoma
Estrogen also drives for proliferation of breast epithelial cells.
It appears that there is a relatively small contribution to the increase in breast cancer
Cured, smoked and pickled foodsIncreased risk for stomach cancers
Japan has a much higher risk for stomach cancer than here
Nitrites found in preserved foodsNitrites are converted to nitrosamines in the liver
Nitrosamines are a very potent carcinogen
Vitamin C may prevent the conversion of nitriles to nitrosamines, evidence not conclusive
AflatoxinOne of the most potent carcinogens known to man
It's a contaminant, a poison produced by molds found on improperly stored peanuts and grains
Causes hepatocellular carcinoma
It causes a mutation in the p53 tumor suppressor gene
Saccharin (artificial sweetener)Shown to cause bladder cancer in rats
The rats were given a high dosage which is unrealistic to what humans consume
No correlation in human populations so no real evidenceVitamin CIs an antioxidant, may decreases risk of stomach cancer (evidence not conclusive)
Vitamin A and beta-caroteneDecreases risk of lung and other epithelial cancers
Vitamin E and seleniumNo known cancer fighting properties
FiberDecreased risk of colon cancer by forcing the movement of food through the colon faster thereby decreasing the amount of time toxins may be in contact with epithelial tissues of the colon.
Increases peristalsis
Environmental risk factor: AlcoholIts related to an increase risk of the following cancers:
Oral cavity
Pharynx
Larynx
Esophagus
Prolonged drinking can lead to cirrhosis of the liver
This is an inflammatory response
Individuals with cirrhosis of the liver will have an increased susceptibility to liver cancer or hepatocellular carcinoma
Many individuals who drink also smoke
Now we have two carcinogens
Moderate alcohol consumption is 1 drink for women and 2 for men a day
Moderate cig smoking is 1-2 packs a day
Mod smoking and Mod drinking each on their own cause an increase of oral and pharyngeal cancer that is 2 times greater than if you don't drink or smoke.
If you do both together you have a 4 fold increase
Heavy drinking is more than 4 drinks a day
Heavy smoking is more than 2 packs a day
Heavy smoking and Heavy drinking each on their own cause an increase of oral and pharyngeal carcinomas about 7 fold
If you do both, 40 times the increased
This is called a synergistic effect
The effects of each is greater than the additive effects of each separately
Environmental risk factor: Tobacco smokeAccounts for nearly 1/3 of all cancer deaths in the United States
It is responsible for 80% of all lung cancers
This contributes about 30% to the death rate
A very significant amount of cancer mortality can be eliminated by eliminating tobacco
Smoking has also been implicated in the following
Cancers of the oral cavity
Cancers of the pharynx
Cancers of the larynx
Cancers of the esophagus
Cancers of the bladder
Canners of the kidney
Cancers of the pancreas
Figure: per capital cigarette consumption vs year vs lung cancer death rate
Lung cancer starts to go up around 1930 as does smoking.
Smoking began in 1910 and 20 years later lung cancer rates go up
That period is known as a Lag Period
This lag period , 20 years, is known to be relatively characteristic of many carcinogens
Many agents take that long, 20 years, for that multistep process of various mutations occurring giving cells increased potential for division/proliferation followed by more aggressive types of tumors appearing
Figure: Annual lung cancer death rates for males and females in the US
Men start smoking in 1910 and lung cancer rates went up in 1930
Women began smoking in the 1940
World War II occurred in 1940 so women filled in the standard typical jobs that men had at home
Not only did they take on mens jobs, they took on their habits to which smoking was probably the worst of all
So 1940 women began smoking and 1960 lung cancer rates go up in women
This is pretty dramatic evidence
The evidence suggests a very strong association between cigarette smoking and lung cancer
It doesn't show that it causes it but it shows a strong association between the two
Some facts:There exists a close dose relationship between cigarette consumption and the development of lung cancer
The more you smoke, the greater your chancers are of getting this disease
The risk for smokers ranged between 5 and 25 times more of that than a non-smoker
Those that are light smokers will have an intermediate risk
Mortality due to cig smoking is enhanced in the presence of other carcinogens
If you stop smoking your rate stops at that point
You have a lower risk of mortality that stops at the point you stop smoking
Over the period of 20 years your chance will go down to almost that of a non-smoker
Chronic installation of tobacco products intraarticularly into experimental animals or exposure of experimental animals to cig smoke will cause them to develop lung cancer
If you expose lung cells in culture to cig smoke they will become transformed
They will under go neoplastic transformation
Now we have both sides, the epidemiologic and the experimental
We can no longer say that cig smoke is associated with lung cancer but we can now say that cig smoke can cause cancer
There are between 2,000-3,000 chemical components and derivative es of those components in a single puff of cig cmoke
Benzopyrine, Nickle carbonyls and dimethyltriosemines are known chemical carcinogens
Benzopyrine has been observed to bind to p53
The risk for pipe smokers, cigar smokers and those who chew tobacco is much greater than a nonsmoker but not as high as a cig smoker
Every time a person puffs a cig it is diluting that stream with 7 volumes of air
If you are standing next to that individual you are getting considerably less
It depends on environment, outdoors vs indoors
Figure: Geographic variation in cancer incidence Colon cancerHighest Incidence: USA
34 cases per 100,000 people
20 times more than india
Lowest Incidence: India
1.8 cases per 1000,000
Prostate cancerHighest Incidence: USA
91 cases per 100,000 people
70 times more than china
Lowest-Incidence: China
1.3 cases per 100,000
MelanomaHighest Incidence: Australia
31 cases per 100,000 people
155 times more than japan
Lowest Incidence: Japan
0.2 cases per 100,000 people
Why is this? There are two possibilities
Populations have exposure to different environmental factors
Populations have genetic variability (they’re genetically different than we are)
We can find out by studying migrant populations
We see that after 1 to 2 generations the patterns become identical indicating that the cancer is based on exposure to environmental factors
The number next to the country with lowest-incidence is referred to as the Minimum Intrinsic Level
The minimum intrinsic level is the lowest level of cancer in a population that cannot be decreased any further. Everything above that is environmentally caused
It is believed that the cancer rate cannot drop below that
Anything above this is environmentally caused
Over 90% of all colorectal carcinomas, on a world wide bases, is environmentally caused.
I have an exam on all this material on monday and much more. Its alot to memorize.. heh. Well, back to my studies, I have another 3 pages of notes to cram into my head. I hope someone finds this educational. I'm enjoying studying it, its just alot to take in!
P.S. If you're interested in more information, mechanisms, more facts etc... I'll be glad to share more of my notes