Реферат: Cancer Essay Research Paper Final Draft T
Cancer Essay, Research Paper
Final Draft T. J. Cox
The problem is cancer. Cancer is the second leading cause of death in the world and my interest in the subject is simple. My mother is the most resilient person I have ever met. Any time I need any kind of inspiration, I need only to think of her. When she was eighteen she was diagnosed with Hodgkin?s disease. The doctors gave her a less than thirty percent chance of living. Since then she has had cancer three other times. Breast cancer twice in ?85 and ?90, and most recently, colon cancer two summers ago. She has had many different treatments including chemo and radiation therapy as well as surgery to remove lumps in both breasts and her colon.
What is cancer? There are more than 100 different types of cancer. It occurs when cells become abnormal and divide without control or order. Normally, cells divide in an orderly way to produce more cells only when the body needs them. If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor, can be benign or malignant. (National Institute of Health)
Benign tumors are not cancer. They do not invade nearby tissue or spread to other parts of the body. Benign tumors usually can be removed and are seldom a threat to life. Malignant tumors are cancer. They can invade and damage nearby tissues and organs. Cancer can also break away from a malignant tumor and enter the bloodstream and lymphatic system.
Through the lymphatic system is one of cancers best modes of transport for spreading to form new tumors in other parts of the body. The spread of cancer is called metastasis. Malignant tumors must be treated or will be fatal.
There are many treatments for cancer. Among these are radiation, chemotherapy, surgery and the rapidly growing field of genetic therapy. It was discovered that when radioactive waves were directed on human cells, the cells would be destroyed. The idea of using this technology on cancer was a good one but was unsuccessful at first due to the damage caused to surrounding tissues. Then the analogy drawn from a simple story gave insight on how to focus the rays on the cancer and not harm the surrounding tissues and organs. The story goes like this.
A small country was ruled from a strong fortress by a dictator. The fortress was situated in the middle of the country, surrounded by farms and villages. Many roads led to the fortress through the countryside. A rebel general vowed to capture the fortress. The general knew that an attack by his entire army would capture the fortress. He gathered his army at the head of one of the roads, ready to launch a full-scale direct attack. However, the general then learned that the dictator had planted mines on each of the roads. The mines were set so that small bodies of men could pass over them safely, since the dictator needed to move his troops and workers to and from the fortress. However, any large force would detonate the mines. Not only would this blow up the road, but it would also destroy many neighboring villages. It therefore seemed impossible to capture the fortress. However, the general devised a simple plan.
He divided his army into small groups and dispatched each group to the head of a different road. When all were ready he gave the signal and each group marched down a different road. Each group continued down its road to the fortress so that the entire army arrived together at the fortress at the same time. In this way, the general was able to capture the fortress and overthrow the dictator.
This simple story was the basis for intensity modulated radiotherapy (IMRT). This is a technique used to treat cancerous tumors on which a removal operation could not be performed. Interesting dose distributions generated by IMRT allow a better sparing of normal tissues with decreased acute and late toxicity, and offer a window for further dose escalation?s. (De Neve W; Claus F; Van Houtte P; Derycke S; De Wagter C) In order to get a radiation beam of high enough intensity to hit the tumor, without damaging surrounding tissues, several lower intensity beams were directed to the tumor from different directions. This method decreases damage to surrounding tissues but, it does not work on all cancer and still has some side effects.
Another method with side effects used to treat cancer is chemotherapy. Chemotherapy is a word to describe chemical agents (drugs) that are used in the treatment of various types of cancer. (Medical Oncology and Hematology Associates) Chemotherapy works by killing rapidly dividing cells. Cancer cells are rapidly dividing, but unfortunately so are white blood cells, red blood cells, platelets, cells lining the mouth, stomach and intestines, hair cells, and reproductive cells. These factors are part of the reason there are so many side effects with chemotherapy. Damage to these other rapidly dividing cells lead to loss of hair, nausea, sore mouth and decreased immune response.
The side effects still associated with radiation and chemotherapy have led many researchers to look to new areas for cures. The breathtaking pace of gene discovery in the last two decades, coupled with the birth of recombinant DNA technology, gave rise to the concept that genes may be manipulated and used as drugs. (Kong HL) Family friend and nationally renown genetic therapist, Ken Culver is working on genetic cures for cancer. One technique he and his team are pioneering is the idea of injecting the genetic code of a curable disease into a cancerous lump via recombinant DNA. The theory is that the disease will take over the cancerous cells and then the lump can be cured by the cure for the disease. Gene therapy has the potential to provide cancer treatments based on novel mechanisms of action with potentially low toxicities. (Roth JA; Swisher SG; Meyn RE)
Many of you have probably heard of cancer patients taking a variety of medicines and varying doses. It has been found that naturally occurring P-glycoproteins help in the build up of resistance to this multidrug technique. In a present study, the pharmokinetics of doxorubicin, a P-glycoprotein modulator, and GF120918, a novel potent P-glycoprotein inhibitor, were examined in cancer patients in a search for more selective modulation of multidrug resistance (MDR). (Sparreboom A., Planting A. S., Jewell R. C., van der Burg M. E., van der Gaast A., de Bruijn P., Loos W. J., Nooter K., Chandler L. H., Paul E. M., Wissel P. S., Verweij J.) Data indicates that GF120918 at the tested doses of combination treatment achieves plasma concentrations that reverse MDR in experimental models and it lacks the significant kinetic interaction with doxorubricin observed previously with other modulators. (7)
Another study found that although multiple genes are involved in carcinogenisis. Carcinogenisis is the mutating of DNA because of a chemical in the body. Mutations of the p53 gene are the most frequent abnormality identified in human tumors. High levels of p53 expression and DNA-damaging agents work synergistcally to induce apoptosis (cell death) in cancer cells. Phase I clinical trials now show that p53 gene replacement therapy using both retroviral and adenoviral vectors(these are ways of getting the replacement genes into the cell) is feasible and safe. (Roth)
Carcinoma, cancer of the epithelial cells, is a major cause of mortality in western societies. Clonal fixation and propagation of genetic changes due to oncogenes(cancer causing genes), sporadically accumulating in the epithelial cells, depend on growth factors and their surface receptors. One of the large families of receptors is that of the ErbB tyrosine kinases. ErbB-2 delays ligand dissociation, enhances coupling to the mitogen-activated protein kinase pathway, and impedes the rate of receptor downregulation. The realization that ErbB-2 is a master regulator of a signaling network that drives epithelial cell prolification identifies this protein as a target for cancer therapy. (Klapper LN; Kirschbaum MH; Sela M; Yarden Y)
Cancer is still the second leading cause of death in the world. All though the outlook on where research is going is optimistic, I still feel that the faith of the patient is large factor. I have had many talks with Ken Culver about patients he has had in the past. One in particular stands out. The patient had a malignant tumor in her lung. She went through every treatment the doctors thought might work and nothing did. The doctors said it was only a matter of time and told her to enjoy the weeks she had left. To their surprise a month later she was improving and after two months the tumor was gone. When they asked her what she had done in the past two months she talked about positive mental imagery. She said she pictured the tumor as a large block of cheese and her immune system as a pack of mice. She envisioned the mice gnawing away on the cheese and she just started feeling better and better. The doctors had no explanation as to how the woman was sitting in the office telling them all this.
Cancer is a horrible disease that effects millions of people every year. Further improvements are being made in past treatment techniques, and new theories are being formulated as we speak. There are so many different types of cancer that there will never be one pill that can be taken as a cure. Hopefully the rapid new findings in gene therapy will be what the world needs to beat the plague of the twentieth century.