Up to this point we have talked about what cancer is, where it comes from, where it starts in the body, the different types of cancer. And reviewed the incidence and mortality facts from around the world and in the United States. In this section we will be talking about the most common cancers that I introduced to you. Let's talk about lung cancer. The lungs sit in the chest and deliver air or oxygen to the blood. Lung cancer is the most common cancer in men and women, approximately 220,000 diagnoses per year in the US. Somewhere between 1.5 and 2 million people are diagnosed worldwide with cancer, and it is an extremely lethal disease. It is the leading cause of cancer death, approximately 160,000 deaths per year in the U.S, and 1.3 million worldwide. We do a very poor job of being able to cure lung cancer, because by the time it's diagnosed, it is too far advanced to be treated locally for cure with surgery or radiation. It is a lethal disease. There are many sub types of lung cancer but 85% of them are called non-small-cell lung cancers or NSCLC. They come in various histologies. Adenocarcinoma is the most common, 40%. But then, there's squamous cell carcinoma and large cell carcinoma. By and large, although we have different histologies for these cancers, they are essentially treated very similarly. On the right you have a picture of lungs, you notice they're very brown. That's because this was a smoker, and you see a big white cancer in the middle of the lung field there. What are the risk factors for lung cancer? Smoking, smoking, smoking. Let me repeat, smoking, smoking, smoking. 87% of lung cancer deaths in men and 70% in women are likely caused by smoking. Risk of developing lung cancer is 25-times higher In smokers as compared to nonsmokers. Many other lung cancers are linked to secondhand smoke. Let me repeat, the number one risk factor for lung cancer is smoking, smoking, smoking. Primary smoking and secondary inhalation of smoke when you are exposed to it. This is why in the United States, smoking has been banned in restaurants and most public places because it is well-known that secondhand smoke is linked to a risk of lung cancer. Other risk factors include radon, asbestos, arsenic, radioactive ores like uranium, and inhaled chemicals. In other words, inhaled substances that damage the lungs. This makes lung cancer prevention fairly straightforward. Stop smoking, do not let yourself be exposed to secondhand smoke. Stop smoking, do not let yourself be exposed to second hand smoke. If you can decrease exposures, for example wearing a air mask if you're a uranium miner, you can decrease your chance of developing lung cancer. So smoking cessation and decreased exposures are the way to prevent lung cancer. Many studies have been done looking to try to understand, can we screen for lung cancer? Many things have been tried, including x-rays and computed tomography scans, and sputum tests. There was a large study, called the National Lung Screening Trial, that looked at men and women 55 to 74 years old who were otherwise in good health, who had at least a 30 pack-year smoking history. That means they smoked at least one pack of cigarettes per day for 30 years. That means they have a 30 pack-year smoking history. If they have smoked half a pack a day for 30 years they would have a 15 pack-year smoking history. If you smoked two packs a day per year it would be a 60-pack year smoking history. The other way to be eligible for this trial was to be still smoking or to have quit smoking within the last 15 years. If a man or woman meets those criteria, it was noted that they could be screened with a CAT scan yearly for three years in a row to look for early lung cancers. And that this could actually detect lung cancers and remove them before they became lethal. So, this is the recommended lung cancer screening but only if you have these characteristics. We do not know how to screen for lung cancer in other populations or for people that potentially have less of a pack year smoking history. Let's move on to colon cancer. The colon is a tube about five feet long at the end of the digestive system that stores waste. So, here in this diagram you can see that you swallow food through esophagus, it lands in the stomach. The stomach then dumps the food into the small intestine. The small intestine further digests the food and then dumps it into the large intestine, which completes the uptake of nutrients and water and also stores the fecal waste. The rectum is the last six inches of the colon. Many people think about Colon cancer, and talk about colorectal cancer, but the rectum really represents a different kind of cancer and we will only be referring, here, to colon cancer. Colon cancer is the third most common cancer diagnosed in men and women. There are approximately 93,000 diagnoses per year in the US. It's the third leading cause of cancer death, approximately 50,000 deaths per year in the United States. Notice there are less deaths, about half the number of deaths as diagnoses per year. That's because if we catch primary colon cancer early, shown here in this picture as an ulcerating mass inside the colon. We can actually remove the cancer with surgery and cure people. Therefore, being diagnosed with colon cancer early, it still can be cured and the deaths are caused by colon cancer that spreads or metastasis. What are the risk factors for colon cancer? Well age. Nine out of ten people diagnosed with colon cancer are over 50 years old. And if you remember I said that the incidents of cancer was going to increase dramatically by the year 2030 from 14 million in 2012 to over 21 million in 2030. That's because the world's population will continue to age as we wipe out diseases that kill children and kill you when you're younger, for example pneumonia and diarreal illnesses. So as the population of the world grows and ages, cancers like colon cancer will be diagnosed more frequently. What other risk factors for colon cancer are there? Diet, a diet high in red meats and low in vegetables. A low fiber diet is a risk factor for developing colon cancer. If you think about it in its simplest terms, if you don't eat vegetables, you don't have a lot of fiber cleaning out the colon as it traverses through, allowing damage to the colon over your lifetime. It's also now noted that lifestyle, obesity, smoking, and alcohol all contribute to a higher risk of colon cancer. Also if you have a history of inflammatory bowel disease, Crohn's disease, or ulcerative colitis, diseases that chronically damage the colon over time, contribute to colon cancer. If you have a positive family history, it's approximately double risk if you have one affected first degree relative. So if you're, have a mother, a father, a sister or a brother who has been diagnosed with colon cancer, your risk is double. There are also several genes that can be inherited that affect your risk of colon cancer. These are genes from a wide variety of families including the DNA repair genes, as KRAS, and P53. You will learn more about these genes in subsequent lectures. Suffice it to say, there are known genes that are risk factors for colon cancer. How to prevent colon cancer? It's very clear that a high fiber diet a low red meat diet is associated with decrease risk of developing colon cancer. In fact I heart healthy diet which is a diet low in red meat, low in fats, and high in vegetables is probably the best way to prevent colon cancer also. So, a person can do much to improve their health, both are risk of having heart disease as well as colon cancer by simply following a heart healthy diet. Another possibility for colon cancer prevention is low-dose aspirin. It's unclear why aspirin is effective. It probably relates to it being an anti-inflammatory, cutting down the chronic inflammation in the colon. But because of risk of bleeding, it is not recommended on a wide basis to be used for colon cancer prevention. The way to screen for colon cancer is very clear. Colonoscopies should be done every 5 to 10 years starting in every person at age 50. This is the most effective way to identify colon cancer early to remove polyps that are on their way to becoming cancer, and is very effective. Other potential tests include stool DNA tests, sigmoidoscopies, barium enemas, and fecal occult blood tests. But quite frankly, they are not being used very often or in a widespread fashion because colonoscopy is so good. The biggest problem with colon cancer screening through colonoscopy is that not everybody follows these guidelines and gets a colonoscopy done. But it is clear that colon cancer incidence and death is decreased by colon cancer screening. What about breast cancer? The breast consists of milk-producing glands surrounded by fat and connective tissue. The glands connect to the ducts, which carry milk out to the nipple. Breast cancer is generally an adenocarcinoma. It develops in the glands themselves and grows out. Here in this picture, you can see a breast cancer that is grown out of the breast and is presenting as a large mass. It is the most common cancer in US women. Approximately 230,000 people are diagnosed per year in the US. Is the second leading cause or cancer death in women approximately 40,000 deaths per year. Again notice the big difference between the number of cases diagnosed and the number of deaths, that's because most of the cancers are diagnosed early enough to be treated with surgery or radiation, which we'll talk about in our last lecture. Which leads to fewer deaths per diagnosed case per year. Again, 80% of primary breast cancers are called infiltrating ductal cancers. They are adenocarcinoma's. There are subtypes like lobular and nipple cancers. But again, the vast majority are adenocarcinomas. What are the risk factors for breast cancer? Again, age. One in eight cancers in women occur under the age of 45, two-thirds over the age of 55. It is clear that family history is important as a risk factor. Having one first-degree relative mother, sister, or daughter with breast cancer doubles a woman's risk. There are genes that are associated with increased risk, known mutations in a woman's genome including breast cancer or BRCA1, which increases risk 55 to 65%. And breast cancer two, or BRCA2, which increases risk approximately 45%. These are genes in the DNA repair pathway and can now be screened for in appropriate populations. Dense breast tissue is also a risk factor, because it makes mammograms, which are screening tests, less accurate. Lifestyle is an important contributor to breast cancer. Obesity, lack of physical activity, alcohol abuse, not having children, oral contraceptive use, and post menopausal hormone therapy all contribute to increasing risk of breast cancer to some extent. The exact number or percent of increased risk is often unclear, but we know that these all contribute. Are there any ways to prevent breast cancer? Well no, there are no known proven strategies except for prophylactic mastectomy in high-risk women. This can be performed in women who for example, have family members who have had breast cancer and who are carriers of those genes BRCA 1 or 2 where it's thought that they have such a high risk of developing breast cancer in the future that the women chooses to have her breast removed. This is not done commonly. Other possibilities for breast cancer prevention include high-fiber, low-fat diets, staying physically active, and maintaining normal weight. You're probably starting to see a theme here, high fiber, low-fat diets, staying physically active, keeping a normal weight not becoming obese, and not smoking are all prevention strategies that cross many cancers. Breast cancers screening consist of monthly self exams by women. Usually at the same time each month of their menstrual cycle. Yearly exams by a health practitioner. And mammograms, which are special x-rays that you'll hear about in a future lecture. There are other radiology techniques, magnetic resonance imaging or ultrasound, that are potentially useful for breast cancer screening, but self-exams, yearly exams, and mammograms remain the gold standard. Let's move on to the prostate, which is a gland about the size of a walnut that sits below the bladder. It is only found in men, and the function of the prostate is that it helps protect the urinary tract from infections. Just like breast cancer is the most common cancer in women, prostate cancer is the most common cancer in men. One in seven men in the US will be diagnosed in their lifetime, approximately 220,000 new cases in the US this year. And it's the second leading cause of cancer death in men, with approximately 27,000 men dying in the US every year. Again, just like with breast cancer, notice the difference in diagnoses versus death. If we find prostate cancer early, before it has spread, it is very curable. In the vast number of men who are diagnosed undergo surgery or radiation to cure their prostate cancer. It's still is the second leading cause of cancer death in men, but there is a vast difference between the number of men diagnosed and the number of men dying in the U.S. every year of this disease. The risk factors for prostate cancer are age, again a disease occurring mainly in older men. Six out of 10 cases are diagnosed to men age 65 or older, and it is rare before age 40. The average age at the time of diagnosis is about 66. Ethnicity place a big role in prostate cancer risk. It is higher in African-American men and your chance of getting prostate cancer is lower if you're Asian. Family history is clearly a risk factor. Having a father or a brother with prostate cancer more than double the man's risk of developing this disease. There are several genes that contribute to prostate cancer risk, including a gene called HoxB13 but also BRCA1 and 2 in men contributes to prostate cancer risk just like they contribute to breast cancer risk in women. A diet high in red meat and low in vegetables also increases prostate cancer risk, just like it did with breast cancer and colon cancer. There are no known prevention strategies for prostate cancer. However, there are, again, possibilities that look very similar to the possibilities for breast cancer, high fiber, low-fat diets, staying physically active, and maintaining normal weight are all thought to contribute to a lower risk of developing prostate cancer. Screening for prostate cancer consists of the yearly digital rectal exam starting at the age 50. We have a test that can help detect prostate cancer called prostate-specific antigen or PSA. Which is a blood test. This is a test that should be discussed with a health provider as a yearly test in men aged 55 to 69. If you are African American or have a positive family history, screening should be discussed with a health care provider to start at age 40. Let's move on to liver cancer. The liver is a large gland that sits right below the rib cage on the right side. This is a very important organ in the body, one that you cannot live without. It processes nutrients absorbed from the intestine. It makes blood clotting factors and it secretes bile for help the body absorb fats. Liver cancer is one of the most common cancers worldwide, with approximately 700,000 new cases diagnosed every year. Mainly in sub Sarahan Africa. In Southeast Asia. It's also a leading cause of cancer death worldwide with approximately 600,000 deaths world wide yearly. Notice how lethal this cancer is because the number of deaths almost equals the number of diagnoses. That's because if liver cancer is usually diagnosed too late to be able to treated with surgery or any other local therapy. In this picture you can see a large mass growing out of the liver. It is generally not detectable until it causes obstruction to bile or some other body system, when it is too late to do anything about it. What are the risk factors for liver cancer? Male sex. Approximately twice as common in men as women. The major risk factors though for liver cancer, involved chronic diseases of the liver. Chronic viral hepatitis, hepatitis B and hepatitis C. These infections lead to cirrhosis, which means scarring, of the liver, which is the biggest risk factor for liver cancer. The chronic damage leads to genetic damage, which leads to liver cancer. Alcohol, when abused, can also lead to cirrhosis. Which then becomes a precursor to liver cancer. Not all patients with cirrhosis get liver cancer but if you do have cirrhosis whether it's from hepatitis B, hepatitis C or alcohol, the risk of developing liver cancer increases dramatically. Hepatitis C and B are endemic to areas of Asia and sub-Saharan Africa and that is why the risk of developing liver cancer is so much higher in those populations. Another common risk factor for liver cancer is exposure to aflatoxin, which is a fungus associated with storing grains in tropical environments. Again, more common in Asia. Lifestyle can contribute to liver cancer. Obesity contributes to cirrhosis. Anabolic steroid abuse and smoking have all been associated with increasing a person's chance of developing liver cancer. This leads to the question of how can liver cancer be prevented? First and foremost, preventing and treating hepatitis infections has become the best way to prevent cirrhosis and prevent the development of liver cancer. Avoiding alcohol abuse, avoiding smoking and avoiding obesity all contribute to liver cancer prevention. Unfortunately, there's no proven strategy for screening for liver cancer. For people at higher risk of liver cancer due to cirrhosis, from any cause or chronic hepatitis, some care givers suggest using a blood tests called the alpha-fetoprotein, which is a protein produced by liver cancers and ultrasound exams every six to 12 months. But there are no firm guidelines. The last major common cancer worldwide that we're going to talk about is stomach cancer. The stomach, it's at the end of the esophagus, just under the diaphragm, and it holds food and starts the process of digestion. Remember it connects to the small intestine, which then connects to the colon. Stomach cancer shown here as an ulcerating mass in the lining of the stomach. Again is extremely common worldwide and not very common in the US. There are approximately 1 million new cases every year centered in Southeast Asia and South and Central America. A leading cause of death, 700,000 deaths worldwide yearly. Again, this is because by the time someone develops symptoms from their stomach cancer, it is spread and it is too late to treat it with primary therapy, such as surgery, for cure. Just like liver cancer, stomach cancer is more common in men. It's more common in people over the age of 60. Over the last 15 years, it has now become evident that chronic infection with the bacteria H pylori appears to cause stomach cancer. H pylori is a bacteria that commonly causes gastritis and ulcers. Ulcers that remain untreated cause further damage to the cells in the lining in the stomach and can lead to stomach cancer. Similarly, a diet that's high in smoked foods, salted fish, and meat, and pickled vegetables, foods that contain high nitrates and nitrites are a major cause of stomach cancer. It is generally thought that the decline in incidence of stomach cancer in the United States is due to, number one, refrigeration, which means that people eat less smoked foods and salted fish and meat, as ways to preserve food as well as good treatment for H pylori, gastritis, and ulcers. Other risk factors for stomach cancer include again lifestyle, obesity, and smoking as well as having a type A blood. But it is unknown why this is a risk factor for stomach cancer. How can we then prevent stomach cancer? Number one, treating H pylori infection, eradicating chronic gastritis as well as stomach ulcers, and using refrigeration instead of salting and pickling, and our old friends high-fiber diet, avoiding smoking, and maintaining a good body weight, all contribute to stomach cancer prevention. Unfortunately, there is no proven strategy for stomach cancer screening. So, we still do not know how to find this cancer and eradicate it worldwide. I just wanted to take a moment to review what we've learned about the major cancers and risk factors. I think it is clear that the number one risk factor for cancers overall is smoking. It's the number one risk factor for lung cancer and is associated with a higher risk of developing virtually every other kind of cancer. In addition, we've seen in this lecture that obesity and diets that are low in fiber and high in red meat also contribute to most cancers. Furthermore, alcohol abuse is a common risk factor across many cancers. So to summarize prevention strategies, don't smoke, don't smoke, don't smoke. And, in addition, being physically active and maintaining a normal weight, as well as eating a heart-healthy diet that is low in red meat and high in fiber are the best ways to decrease risk of developing cancer. Thank you for listening to this first lecture in The Introduction to Cancer Biology course. I hope it is given you a perspective on how cancer came to be named. What the risk factors for cancer are, where its starts in the body, and some of the screening and preventions strategies that are currently available. Future lectures will go into much more detail about the genetic cause of cancer, the different hallmarks of cancer as well as how we diagnose cancer and how we treat it. Thank you very much. [MUSIC]
