Page 62 Complete Your CE Test Online - Click Here 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 six percent of cancers, with an even higher rate of missing adenomatous polyps (pre-cancerous lesions) [42]. Adequacy of colonoscopy preparation is cited for some of this problem, as stool can obscure the view of the colon wall [41]. 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 [165]. Overdiagnosis and overtreatment Historically, the word “cancer” has meant a disease that ended in death if untreated. While 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 healthcare 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 [301]. 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 or her lifetime [134]. For example, in much older people, especially those with co- morbidities, 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 [304]. 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 they actively discourage 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 [295]. 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 [142]. A closer look reveals this example: when a woman is diagnosed with ductal carcinoma in situ (DCIS), she often ends with a mastectomy. But DCIS is considered a Stage 0 cancer (see “Cancer Staging”) – a non-invasive cancer very unlikely to progress to a lethal condition. More than 60,000 women are expected to be diagnosed with it in 2016 alone [122]. Recommended screening tests for cancer by cancer site Colorectal cancer screening There is a range of testing options for colorectal cancer (CRC) screening. See below for specifics and recommendations for each. Colonoscopy and sigmoidoscopy also help prevent CRC because they can detect polyps that can be removed before they develop into cancer. CRC risk increases dramatically with age: 90% of all colorectal cancers are diagnosed after age 50, and 93% of CRC deaths occur after that age [19]. Expert groups generally recommend that people who are at average risk for CRC have screening from ages 50 through 75 [191]. Screening can detect CRC earlier and impact survival The five-year relative survival for localized CRC is 90%, but only 40% of people are diagnosed at this stage, in part because screening is underused. In contrast, five-year relative survival for people with regional CRC is 70%; for those with distant metastases, it is 13% [19]. Nursing consideration: Help patients reduce colorectal cancer mortality risk or even prevent colon cancer by educating them about different colorectal cancer screening options. Help them choose an option that they might actually follow. Most patients will still need screening after cancer treatment, though options will be different if cancer involved the colon or rectum [191]. High-sensitivity fecal occult blood tests (FOBT) Both polyps and colorectal cancers can bleed, and FOBT checks for tiny amounts of blood in feces that cannot be seen. Blood in stool may also indicate the presence of non-cancerous conditions such as hemorrhoids, but should never be assumed to be the cause when an FOBT is positive. Two types of FOBT are approved by the U.S. FDA to screen for colorectal cancer: the older guaiac FOBT, or gFOBT; and the fecal immunochemical (or immunohistochemical) test, or FIT, and also known as iFOBT. With both types of FOBT, stool samples are collected by the patient using a kit, and the samples are returned to the doctor. Note that tests are performed using stool that remains on a gloved finger after a rectal exam are not adequate for screening [11]: ● ● Guaiac FOBT uses a chemical to detect heme, a component of hemoglobin. Because the guaiac FOBT can also detect heme in some foods (e.g., red meat), people have to avoid certain foods before having this test. ● ● FIT uses antibodies to detect human hemoglobin specifically. Dietary restrictions are typically not required for FIT [54,234]. Studies have shown that guaiac FOBT, when performed every one to two years in people aged 50 to 80 can reduce the number of deaths due to colorectal cancer by 15-33% [54,234]. If FOBT is the only type of colorectal cancer screening test performed, the U.S. Preventive Services Task Force recommends yearly testing [290]. The American Cancer Society notes that it is slightly more effective when a sigmoidoscopy every five years is added to the annual FOBT for people of average risk [29]. The American Cancer Society further notes that patients with an abnormal FOBT will need a colonoscopy [11]. Sigmoidoscopy In this test, the rectum and sigmoid colon are examined using a sigmoidoscope, a flexible lighted tube with a lens for viewing and a tool for removing tissue. This instrument is inserted through the anus