Page 40 nursing.elitecme.com Complete Your CE Test Online - Click Here wide-ranging vision and careful consideration. Even with these caveats, a surprising number of groups participate. Some physician groups make recommendations within their practice areas (e.g., the American Congress of Obstetricians and Gynecologists and the American College of Gastroenterology). Even cancer treatment centers will have their own interpretations of cancer screening guidelines. So when health professionals speak of cancer screening guidelines, it is important to know which guidelines are under discussion. This section will focus on the best-known national groups that have been making broad cancer screening recommendations for many years. These include the U.S. Preventive Services Task Force (an independent panel of volunteer health experts since 1984) and the American Cancer Society (a donor-supported nonprofit since 1913). Both are reputable and well respected. Their cancer screening recommendations are different in a few places but agree on many points. Sometimes the differences are based on how certain research findings are valued or weighted and often indicate issues that need more research or consideration. Health care providers can choose options from one or the other set of cancer screening guidelines based on the patient’s values and preferences, health insurance situation, and even what is available in the geographic area. Screening recommendations change from time to time as new tests are studied and new evidence comes in to support or counterbalance the older studies. It is a good idea to visit these websites (http://www. uspreventiveservicestaskforce.org and http://www.cancer.org) and review their cancer screening guidelines at least once a year to find out what changed. Limitations of cancer screening Even the best cancer screening tests are imperfect and fail to detect every case of cancer. Sometimes abnormalities are found that are not cancer. Several screening tests have been shown to be fairly reliable at detecting cancer early and reducing the chances of dying from that cancer. Other screening tests have been shown to detect cancer early but less reliably. Some cancer screening tests work well in the hands of experienced health care providers but not so well in those who are new to it or who do not do it often. And others may be reliable enough but have not yet been shown to reduce the risk of death overall. In some cases, the screening is too new for research to have been conducted, but in other cases, the research has been done but has not shown improvement in the death rate from cancer. Reducing the death rate is the gold standard for cancer screening tests. Higher levels of cancer risk may modified screening methods The screening guidelines discussed most often are aimed at people of average cancer risk, and health professionals may have to look to source documents to find the most recent recommendations for higher risk patients. Professionals also have to verify what constitutes high risk because not every factor that may seem relevant has been shown to truly increase cancer risk. People at high risk of certain types of cancers may need to start screening at younger ages, have more frequent screening tests, or even have extra screening tests than those at average risk of cancer. It is also important to know that even the most innocuous cancer screening tests have potential harms as well as benefits. False-positive tests An obvious concern is a false-positive result, in which the test suggests cancer is present even when it is not. False-positive tests can cause stress and anxiety, and often require follow-up testing and procedures that are more invasive and have more potential harm. The ability of a test to exclude people who do not have the condition (or only give true positives) is called specificity. The concern in this case is that the follow-up procedures following the positive test are more invasive and more likely to have complications than the screening test itself. For example, a positive mammogram may require a breast biopsy. A positive stool fecal occult blood test (FOBT) or fecal immunochemical test (FIT) typically requires a colonoscopy for follow-up, which might include polyp removal and biopsy. Positive Pap tests often require colposcopy and sometimes biopsy procedures. Less obviously, biopsies may result in finding a low-grade cancer that might be treated even though it would be unlikely to cause problems in the person’s lifetime. Technically, this is a true positive (it is a true case of cancer), but its treatment might be unnecessary (see “Overdiagnosis and Overtreatment” for discussion). False-negative tests Less obvious but possibly more concerning are false-negative tests. The test can sometimes indicate that cancer is not present even though it is actually present. False-negative test results may provide false reassurance and lead to delayed diagnosis. A false-negative result may prompt a patient to postpone seeking medical care even if symptoms develop. The ability of a test to detect a condition when it exists is called sensitivity. Colonoscopies, despite being the gold standard for colon and rectal cancer screening, have been reported to miss as many as 6% of cancers, with an even higher rate of missing adenomatous polyps (precancerous lesions). Adequacy of colonoscopy preparation is cited for some of this problem, as stool can obscure the view of the colon wall. Some sources also cite higher rates of missing polyps that are flat or depressed. Although we may think of polyps as raised or pedunculated, some are not. Large, flat, and depressed lesions may be more likely to be severely dysplastic, although this remains under study. Overdiagnosis and overtreatment Historically, the word cancer has meant a disease that ended in death if untreated. Although this was mostly true at a time in history when people were diagnosed with cancer because they had signs or symptoms, it began to change when health care professionals became able to detect cancer while still asymptomatic. One of the ways overdiagnosis was noticed was that the death rates from certain cancers found early did not always decline, or they did not decline at a rate commensurate with the rise in cases detected. Scientists and health professionals are starting to understand that despite historical assumptions, some cancers grow quickly, some grow slowly, and some may even stop growing spontaneously. This is a confusing concept for health care providers and the public alike. Overdiagnosis happens when a test correctly shows that a person has cancer, but the cancer that is found is a slow-growing type that would not likely have harmed that person in his lifetime. For example, in much older people, especially those with comorbidities, a slow- growing cancer is likely to be outpaced by another illness. It is becoming clear that a number of people who are screened actually have low-grade cancers unlikely to cause serious harm or death. Treatment of such cancers is called overtreatment, which in many cases causes real and lasting harm. So far, this trend is showing up in retrospect because it can be difficult to predict whether any one person’s cancer is likely to spread and cause health problems or death. The observation is already changing screening guidelines in the U.S. After prostate cancer screening was re-evaluated in light of this kind of evidence, the American Cancer Society recommendations changed from universal screening with prostate-specific antigen (PSA) tests to discussing prostate cancer screening with the patient. The patient and provider ideally make a shared decision about screening based on informed consent, including the patient’s history and priorities for care, before offering PSA testing. However, the U.S. Preventive Services Task Force went so far as to recommend against screening with PSA tests for prostate cancer. This means that it actively discourages using PSA screening in general, although with the addendum that it should not be offered without discussion of harms and a fully informed choice by the patient. This implies that it could be offered to men who understand and choose to get the screening, but that the test should not be routine. Right now, cancer researchers and public health experts are starting to talk about breast cancer screening. Mammograms have clearly been shown to reduce the death rate from breast cancer in women 40 and older, but they do not reduce this rate as much as predicted. The National Cancer Institute notes that although there are uncertainties in determining the rate of overdiagnosis in breast cancer, long-term, well-conducted studies on excess incidence found that at least 20% of screening-detected breast cancers are likely overdiagnosed.