What is Cancer?
Cancer is a disease in which cells grow and divide uncontrollably, damaging the parts of the body around them. A cancer tumor begins as a single cell. A _________nucleusmutationcell in the cell's DNA disrupts the normal cell cycle. Cancer cells can overrun normal cells.
Cancer is actually not just one _________diseasecellmutation. In fact, there are more than _________1050100 types of cancer. Cancer can occur in almost any part of the body. Cancers are often named by the place in the body where they begin.
How Cancer Begins
Scientists think that cancer begins when something damages a portion of the DNA, causing a mutation. Damage to the _________cytoplasmribosomesDNA can cause cells to function abnormally. Cells that go through the cell cycle divide in a controlled way. Cancer begins when mutations disrupt the normal cell cycle, causing cells to divide in _________a slow wayan uncontrolled waya normal way. Without the normal controls on the cell cycle, the cells grow too large and divide too often.
At first, one cell develops in an abnormal way. As the cell divides over and over, the repeated divisions produce more and more abnormal cells. In time, these cells form a tumor. A _________tumorcellorgan is a mass of _________normal largeabnormal cells that develops when cancerous cells divide and grow uncontrollably.
How Cancer Spreads
Tumors often take _________daysweeksyears to grow to a noticeable size. During that time, the cells become more and more abnormal as they continue to divide. Some of the _________cancerousnormalsmall cells may break off the tumor and enter the bloodstream. In this way, the cancer can spread to other areas of the body.
Treating and Preventing Cancer
There are _________thirtyhundredsthree common ways to treat cancer: surgery, radiation, and drugs that destroy the cancer cells. When cancer is detected before it has spread to other parts of the body, _________surgerychemotherapyradiation is usually the best treatment. If, however, the cancer has spread, or if the tumor cannot be removed, doctors may use _________surgerychemotherapyradiation. Radiation consists of beams of high-energy waves. Fast-growing cancer cells are more likely than normal cells to be destroyed by radiation.
Chemotherapy is another form of cancer treatment. _________SurgeryChemotherapyRadiation is the use of drugs to treat a disease. Cancer treatment drugs are carried throughout the body by the bloodstream. These drugs kill cancer cells or slow their growth.
People can reduce their chances of developing cancer by avoiding smoking, eating a healthful diet, and protecting their skin from bright sunlight. When people inhale tobacco smoke, lung cancer and other forms of cancer may result. Unhealthful diets may lead to almost as many cancer deaths as does tobacco. A diet high in _________fatty foodsproteincarbohydrates, such as fatty meats and fried foods, is especially harmful. Eating a lot of fruits and vegetables may help lower the risk for some types of cancer.
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