recommendations have been created to help individuals and their health care providers decide together whether an individual should be screened for cancer, at what age the screening should start, how frequently the screening should be done and by which method, and if and at what age the screening should stop. Routine screening aims to catch precancerous lesions or cancer at an early stage when they can be treated more effectively, thus reducing cancer-related deaths (see Figure 10, p. 55) (274). Accruing evidence suggests that recommended cancer screening lowers cancer mortality. In a recent study, researchers analyzed the rate of lung cancer-related mortality from eight clinical trials comprising more than 90,000 participants who received lung cancer screening using either the low-dose computed tomography (LDCT) or chest radiography, or who did not receive lung cancer screening (275). Findings showed a 21 percent reduction in lung cancer-related deaths in participants who were screened for lung cancer using LDCT, compared to the other two groups. Despite the evidence of the benefits, uptake of the recommended lung cancer screening remains suboptimal among eligible individuals (see Sidebar 22, p. 63). It is equally vital to receive follow-up testing if the screening test is abnormal, which may indicate the presence of precancerous lesions or cancer. There is strong evidence that many people do not receive follow-up testing after a positive screening test (see Sidebar 22, p. 63). One study examined data from more than 32,000 average-risk individuals who had received a positive result from stoolbased screening for colorectal cancer between 2017 and 2020. Researchers found that only 53.4 percent received follow-up colonoscopy within one year of receiving the positive result from the initial screening test (276). This is unfortunate considering recent data, which show that not receiving the follow-up colonoscopy after a positive stool-based test doubles the risk of dying from colorectal cancer (277). A modeling study estimated a 16 to 23 percent reduction in colorectal cancer-related deaths among individuals who followed up with colonoscopy after a positive stool-based test (278). These findings highlight the importance of receiving follow-up testing after an abnormal screening test. What Can Cancer Screening Find and What Can Be Done? When a person undergoes cancer screening, the test result could be negative, positive, indeterminate, or incomplete. When the screening test does not indicate an abnormality, the person should continue routine screening in close consultation with a clinician as long as the benefits of routine cancer screening for the individual continue to outweigh potential harms. If the test detects a precancerous lesion, the lesion can be treated, thus minimizing the likelihood of its progression into cancer. If the test finds a cancer at an early stage of development, for example, stage I or stage II for a solid tumor, the patient can be treated successfully and has a higher likelihood of a cure. Treatment is less likely to be curative if cancer is detected at a later stage of development, i.e., stage III or stage IV. Treating a precancerous lesion or cancer at the earliest stage of development is called cancer interception, which is an area of active research for its potential to minimize the burden of cancer. Adapted from (1). FIGURE 10 Node INCREASING TIME AND NUMBER OF MUTATIONS Normal Precancerous Lesion Cancer is detected at an early stage. Treat as appropriate for the type of cancer and the exact stage of disease at diagnosis. Remove precancerous lesion to prevent cancer development. Nothing abnormal detected. Continue routine screening. Cancer is detected at a late stage. Treat as appropriate for the type of cancer and the exact stage of the disease at diagnosis. Tumor Localized Early Locally Advanced Late Locally Advanced Metastasized TIME Metastasis STAGE I STAGE II STAGE III STAGE IV Screening for Early Detection AACR Cancer Progress Report 2023 55
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