Page 5 Complete Your CE Test Online - Click Here 6. Angiogenesis: Micrometastases stimulate the growth of new blood vessels to obtain a blood supply. A blood supply is needed to obtain the oxygen and nutrients necessary for continued tumor growth. Because cancers of the lymphatic system or the blood system are already present inside lymph vessels, lymph nodes, or blood vessels, not all of these steps are required for their metastasis. The ability of a cancer cell to metastasize successfully depends on the following: ● ● The cell’s individual properties. ● ● The properties of the noncancerous cells, including immune system cells, present at the primary cancer site. ● ● The properties of the cells it encounters in the lymphatic system or the bloodstream and at the final destination in another part of the body. Not all cancer cells, by themselves, have the ability to metastasize. In addition, noncancerous cells at the primary site may be able to block cancer cell metastasis. Successfully reaching another location in the body does not guarantee that a metastatic tumor will form. Metastatic cancer cells can lie dormant at a distant site for many years before they begin to grow, if they are able to grow at all. Cancer development is a multistep process, and there are many “roadblocks” that may or may not be overcome by the cancer cells. This is why cancer development can take such a long time. Symptoms of metastatic cancer Some people with metastatic tumors do not have symptoms and the metastases are found by X-rays or scans. When symptoms of metastatic cancer occur, their type and frequency depend on the size and location of the metastasis. For example, cancer that spreads to the bone is likely to cause pain and can lead to fractures. Cancer that spreads to the brain can cause a variety of symptoms, including headaches, seizures, and unsteadiness. Shortness of breath or dyspnea on exertion may be signs of lung metastasis. Abdominal swelling or jaundice can suggest that cancer has spread to the liver. Sometimes a patient’s primary cancer is discovered only after a metastatic tumor causes symptoms. In most cases, when a metastatic tumor is found, the primary cancer is also found. The search for the primary cancer may involve lab tests, X-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, positron emission tomography (PET) scans, and other diagnostics. In some patients, a metastatic tumor is diagnosed, but the primary tumor cannot be found despite extensive tests. The pathologist knows that the diagnosed tumor is a metastasis because the cells do not look like those of the organ or tissue in which the tumor was found. Doctors refer to the primary cancer as unknown or occult, and the patient is said to have cancer of unknown primary (CUP). Because diagnostic techniques are constantly improving, the incidence of CUP is decreasing. Even though CUP can be treated with a number of cancer treatments, cure is generally unlikely because the cancer typically has multiple metastatic sites. CAUSES OF CANCER Cancer can be caused or promoted by external exposures or events, such as smoking, ultraviolet radiation, and medications that suppress the immune system. Cancer can also be caused by other health conditions or problems, including inherited and acquired genetic mutations; the internal hormonal environment; and poor immune function. These kinds of exposures and conditions can act synergistically or in sequence to initiate and promote cancer growth. When there is exposure to a carcinogenic event or substance, it is common for 10 or more years to elapse between the exposure and the cancer diagnosis, although it is often much longer than a decade (see “Cancer Risks and Carcinogens”). This latency period varies by type of exposure and type of cancer as well as other factors. It is very difficult in a given cancer case to pinpoint any one cause. More commonly, health care professionals can point to only a group of risk factors as the most likely to have affected the patient’s development of cancer. Sometimes, there are few known risk factors for a person’s cancer beyond older age and sex. When patients and families want to know about cancer and links to causality, they often do not know where to look for reliable information. Information from the Internet or other sources can be unreliable. Many unfounded theories pose as facts on the Internet and social media. Health care professionals can look at reliable sources, such as PubMed, to find out whether an actual peer-reviewed study has been published and what kind of link is postulated (see section, “Resources for Nurses”). A lot of the information easily found online has no reliable study associated with it. Although a site or post may refer to “research” or “studies,” it is often the case that no citations are given. Unfortunately, even if there are studies, most research does not examine causality; many widely publicized studies are strictly observational. If a study is researching only correlations, it might report, for instance, that weight loss is correlated with cancer, or with death. This would certainly sound familiar to nurses because most people lose weight when they have cancer or another serious illness. However, this is statistically termed confounding. Incredulously, some study reports confuse things like this, in this case implying that poor nutrition was the cause of the illness and death. Illness caused the weight loss and not the other way around. Although this may seem like a silly example, nonmedical writers often do not understand such obvious issues as reverse causality or confounding. And even statisticians do not always know about basic anatomical processes, such as cachexia of chronic disease. Cancer risk factors and carcinogens Cancer risk factors include exposure to chemicals or other substances, as well as certain behaviors. They include things people cannot control, such as age and family history. Other risks can be controlled. Likewise, some carcinogens can be avoided, but others cannot. Limiting exposure to avoidable risk factors may lower the risk of developing certain cancers. Lifestyle, diet, and exercise Obesity People who are obese may have an increased risk of several types of cancer, including cancers of the breast (in women who have been through menopause), colon, rectum, endometrium, esophagus, kidney, pancreas, and gallbladder. Conversely, eating a healthy diet, being physically active, and maintaining a healthy weight may help reduce risk of some cancers. These healthy behaviors also help to lessen the risk of some other illnesses, such as heart disease, type 2 diabetes, and high blood pressure (see section “Cancer Prevention”). Tobacco Decades of research have consistently established a strong causal link between tobacco use and cancers. Smoking is associated with one out of every three cancer deaths (32%), and four out of every five lung cancer deaths (80%). Cardiovascular disease, heart attacks, strokes, COPD, ectopic pregnancy, erectile dysfunction, and gingivitis are other health risks that are elevated for tobacco users. According to the National Cancer Institute (NCI), cigarette smoking is strongly correlated with the following cancers or cancer sites: ● ● Lung. ● ● Oral cavity. ● ● Pharynx. ● ● Larynx. ● ● Esophagus. ● ● Bladder. ● ● Kidney. ● ● Pancreas. ● ● Stomach. ● ● Cervix. ● ● Acute myelogenous leukemia. The NCI notes that the body of evidence confirming these links is substantial. Further support is demonstrated by the lung cancer death rates in the U.S., which have mirrored smoking patterns. The risks of lung cancer from smoking are dose dependent and increase markedly by