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Our cells, like everything else, are made up of chemicals. Some chemicals are very stable and can last for years (or many thousands of years) without changing. They do not interact with other things and stay just like they are. Radicals are chemicals that are unstable, they can easily interact with other chemicals, changing both of them. Free radicals are small unstable chemicals that can be found in our cells. Because they can react with other things, they can cause damage to important cell parts. Of particular importance is the genetic material (DNA) in cells. Free radicals can be created by exposure of cells to radiation, or be formed by the breakdown of other chemicals. Cells of the immune system produce free radicals in their efforts to get rid of invading organisms (like bacteria).
Antioxidants are chemicals that can combine with free radicals, like a missile interceptor. Antioxidants can 'take the hit' for the rest of the cell, preventing damage to important proteins, and the genetic material.
Their have been several studies looking at the ability of different antioxidants to prevent cancer as well as using antioxidants along with cancer treatments. The results are not always clear and sometimes, the results have shown that antioxidants can cause problems. Examples of antioxidants include vitamin E and vitamin C.
ALL cancers involve the loss of tumor suppressors. The systems controlled by a tumor suppressor called p53 are broken in essentially all cases of cancer. There are some cancers that run in families (familial cancers), that are due to defects in tumor suppressors. An example is the eye cancer, retinoblastoma. This cancer affects children and is passed down through families.
Affected people inherit one defective copy of a tumor suppressor called Rb (for retinoblastoma). Humans have two copies of most genes in their cells, so if people that inherit one bad copy lose the other, they are very likely to develop cancer. This is the case in familial retinoblastoma. Another familial cancer due to defective tumor suppressors is a form of colon cancer called Famial Adenomatous Polyposis (FAP). These patients develop many polyps in their colons, some of which become cancerous. http://www.cancerquest.org/introduction-tumor-suppressors.html
A good analogy for a cell is a car. They are little machines and have a 'gas' system and a 'brake' system. The genes of the gas system make cells divide or help them survive. The genes of the brake system slow growth or cause cells to die when they are abnormal. Tumor suppressor genes are the 'brakes'. The majority of tumor suppressors are responsible for detecting damage in cells and then preventing damaged cells from reproducing. Others are involved in triggering the cellular version of suicide, a form of cell death called apoptosis (AH-PUH-TOE-SIS or A-POP-TOE-SIS). By blocking the reproduction (or killing) defective cells, tumor suppressors can prevent the development of cancer.
Cancer genes are just regular genes that have been identified as contributing to cancer development or spread. Importantly, they do this only when they are NOT WORKING the way they are supposed to. Many genes have been identified already and more are found all the time. 'Cancer genes' generally fall into one of a two main categories:
1. Tumor suppressors: These genes produce products that slow/block cell reproduction or cause defective cells to die. Some tumor suppressors are involved in protecting DNA from damage. These genes represent the 'brake system' of our cells.
2. Oncogenes: These genes are the cellular equivalent of a 'gas system' and they cause cells to reproduce, avoid cell death, help cancer cells spread, or lead to drug resistance.
Until very recently, proteins were the main products of interest from tumor suppressor genes and oncogenes. Now, we are learning that there are many small nucleic acids that can control cell behaviors. These microRNAs (miRNA) are being very actively studied. Learn more:http://www.cancerquest.org/introduction-to-micrornas.html
The actual process that cancer cells use to divide is the same as normal cells, but the CONTROLS on the process are different. Normal cells only divide when they are 'told' to do so, but cancer cells divide without appropriate signals. They also don't stop when normal cells would. As an example, normal cells will stop dividing when they are surrounded on all sides by other cells (a kind of crowd control). Cancer cells don’t stop and pile up to form piles that can turn into tumors. Another key thing is that cancer cells will continue to reproduce even if their genes are badly damaged. This leads to more and more abnormal cells.
This is a very active area of research. One of the key features of cancer cells is that they are genetically unstable. That means that their DNA gains many mutations over time. As a result of this damage, cancer cells behave differently as time goes on. In an original tumor, SOME of the cells gain the ability to begin moving and invading nearby areas. To do this, they have to produce different kinds of molecular 'scissors' to cut through tissue and invade. Of the cells that gain the ability to move and invade, some will make it to distant areas of the body. To live in this new location, the cells have to adapt to the new environment. To a cancer cell, the organs of the body are very different from each other. A breast cancer cell moving to the lungs would be like taking a person from Florida and plopping them down in Alaska. They would have to adapt or they would die. In cancer, both things happen. MOST cells that move actually die, only a few have the 'skills' needed to survive the trip and grow in a new place. Importantly, cancer cells can get help from other, non-cancerous, cells in the new location. The 'helper' cells are not doing anything 'bad' on purpose, they are just tricked by the cancer cells into helping out.http://www.cancerquest.org/how-cancer-spreads-introduction.html
Metastasis is the spread of cancer from its original location to other areas in the body. Cancer cells frequently travel to other areas by getting into the blood circulatory system or the lymphatic system. These 'highways' can carry the cells all around the body. Also, cancer cells can spread to nearby organs when/where the organs contact each other. The process of spreading is called metastasis and the tumors that grow at the new location are called metastases (often abbreviated as 'mets'). Cancer that has spread is more difficult to treat because it can no longer all be removed by surgery. Also, not all parts of the body are easily reached by the drugs used to treat cancer. As an example, many drugs have a hard time getting into the brain. About 9 out of 10 cancer deaths are caused by cancer that has metastasized.http://www.cancerquest.org/how-cancer-spreads-introduction.html
I was going to write an answer but then I found a great write-up on the Novartis website (http://www.novartisoncology.com/patients-caregivers/what-is-cancer/bone-metastasis-symptoms.jsp). The following is a direct quote from their site
Bone pain. Pain is the most common symptom of bone metastasis and is usually the first symptom that patients notice. At first the pain may come and go. It tends to be worse at night or with bed rest. Eventually the pain may increase and become severe. Not all pain indicates metastasis. The doctor can help you distinguish between pain from metastasis and aches and pains from other sources. Fractures. Bone metastasis can weaken bones, putting them at risk for fractures. In some cases a fracture is the first sign of bone metastasis. The long bones of the arms and legs and the bones of the spine are the most common sites of fracture. A sudden pain in the middle of the back may indicate a cancerous bone breaking and collapsing. Spinal cord compression. When cancer metastasizes to the spine, it can squeeze the spinal cord. The pressure on the spinal cord may not only cause pain, it may cause numbness or weakness in the legs, problems with the bowels or bladder (for example, trouble urinating), or numbness in the abdominal area. High blood calcium levels. High levels of calcium in the blood (hypercalcemia) are caused when calcium is released from the bones. High calcium levels may reduce one's appetite, may cause nausea, thirst, constipation, tiredness and confusion. If untreated, it may cause a coma. Other symptoms. If bone metastasis affects the bone marrow, other symptoms may be experienced, depending on the type of blood cell affected. Red blood levels may drop, causing anemia that leads to symptoms of tiredness, weakness and shortness of breath. If white blood cells are affected, the patient may develop infections that cause fevers, chills, fatigue or pain. If the number of platelets drops, abnormal bleeding may occur.
Hard question to answer. Detection of the spread (metastasis) of cancer is dependent on how large the metastatic growths are and how quickly the cancer cells are multiplying.
Two common tools used to find metastatic cancer are CT (computed tomography) scans,a type of X-ray that captures many images that are then combined into a three dimensional reproduction and PET (positron emission tomography) scans. PET scans involve the injection of a radioactive material (usually a sugar) that can be taken up by cancer cells. Since the cancer cells are dividing quickly they take up more of the sugar and can be seen on images that pinpoint sites where the sugar accumulates.
It is also possible to directly get samples (biopsies) of some areas.
I am not sure if you are referring to cancer prevention or survival. That being said, all the studies I have seen indicate that exercise is beneficial. In part, this is likely due to weight loss. It is hard to tell what part of the benefit is due to the exercise and what part is due to the reduced risk associated with a lower body mass index (BMI).
If you want to see some of the scientific articles on this, go to PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) and search on 'breast cancer survival exercise' or 'breast cancer prevention exercise'. You will see many results. As always you need to be careful when reading articles to pay attention to 1) the source of funding and 2) the number of people in the study.
We have a large amount of information about breast cancer on our website, CancerQuest (http://www.cancerquest.org)
Yes, early exposure to sunlight (i.e. UV radiation) increases risk for melanoma. The following was taken from PubMed:
Cancer Causes Control. 2001 Jan;12(1):69-82. Childhood sun exposure as a risk factor for melanoma: a systematic review of epidemiologic studies. Whiteman DC, Whiteman CA, Green AC. Source
Epidemiology and Population Health Unit, Queensland Institute of Medical Research, Brisbane, Australia. daveW@qimr.edu.au Abstract OBJECTIVE:
To review the evidence that childhood is a period of particular susceptibility to the carcinogenic effects of solar radiation. METHODS:
Studies were identified through searches of computerized bibliographic databases and article reference lists. Eligible studies were those that reported risks of melanoma associated with sun exposure during two or more age-periods. RESULTS:
The measurement of childhood sun exposure varied across studies, preventing formal meta-analysis for most measures. We found that the way in which sun exposure was measured led to strikingly different conclusions regarding the association between age-specific sun exposure and risk of melanoma. Ecological studies assessing ambient sun exposure consistently reported lower risks of melanoma among people who resided in a low ultraviolet (UV) environment in childhood compared with those who resided in a high UV environment. In contrast, case-control studies differed widely in their findings, and no consistent associations with childhood sun exposure were observed.
Ecological studies provided better-quality evidence than case-control studies for examining the effects of exposure to sunlight during specific age periods. Exposure to high levels of sunlight in childhood is a strong determinant of melanoma risk, but sun exposure in adulthood also plays a role.
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