Despite widespread awareness of the importance of screening for asymptomatic, early detection of cancer, screening tests exist for only five cancer types. With few recommended cancer screening tests and generally low adherence to cancer screening recommendations, it is difficult to detect cancer before symptoms arise or before cancers have metastasized. According to new research from NORC at the University of Chicago, only 14% of cancers in the United States are diagnosed after the patient had a recommended screening test, whereas the vast majority of cancers are found by other means, including when symptoms occur or pursuant to other medical care.
Researchers at NORC conducted the first-ever analysis to determine the percentage of cancers detected by screening. When cancer is detected in earlier stages, survival rates are four times higher compared to late-stage detection.
Only four types of cancer—breast, cervical, colorectal, and lung—have a screening test recommended by the United States Preventive Services Task Force (USPSTF). These cancers make up 29% of all U.S. cancer cases. However, many people do not consistently receive recommended screenings, and 15% of all diagnosed cancers are these four cancers that have screening tests, but patients did not receive them. A fifth cancer—prostate—has a screening test that is not broadly recommended due to overdiagnosis.
Research Methodology
The study estimated the overall percentage of cancers detected by screening (PCDS) in the United States in 2017 with a primary focus on the four specific cancer screening programs for which population screening is recommended by the USPSTF, as well as the PCDS for prostate cancer. For breast, cervical, and colorectal cancers, the PCDS is the product of the screening rate and the expected number of cancers detected per screening, divided by the overall cancer incidence. The screening rate is estimated as the national, self-reported screening rate for the prior 12 months from the CDC’s National Health Interview Survey database. Prostate cancer PCDS reflects the percent of all diagnosed prostate cancers that were diagnosed as grade 1 (“well differentiated”) or 2 (“moderately differentiated”), encompassing cancers with a Gleason score of 2 through 6. PCDS estimates for lung cancer are based on 2017 results from a published paper using data from The American College of Radiology’s Lung Cancer Screening Registry. Results were presented at the state level without stratification by age and sex.
According to NORC estimates, 57% of all diagnosed cancers currently do not have a recommended screening test. These cancers are typically found in patients who are symptomatic, perhaps with cancers in later stages that are more difficult to treat. In total, these diagnoses account for 70% of cancer-related deaths.
“Cancer treatments have vastly improved over the last few decades, but the health system’s ability to screen for cancer, which is essential for early diagnosis and effective treatment, still has a long way to go,” said Caroline Pearson, Senior Vice President at NORC at the University of Chicago. “There need to be more screening options to catch more cancers and improve outcomes for patients.”
The percentage of patients who receive recommended screening and the effectiveness of those screenings impacts the percent of cancers detected by screening, across cancer types. For example, 61% of breast cancers are detected by screening, while just 3% of lung cancers are detected. Experts from NORC at the University of Chicago said these differences are the result of varying incidence and screening rates; for example, breast cancer screening rates range from 43.6% to 56.9%.
“To achieve our national goals to improve cancer care, we need better data about cancer screening and diagnosis, especially reliable data by race and ethnic group,” said Ms. Pearson.
To learn more about the percentage of cancers detected by screening and to explore state-by-state estimates, visit cancerdetection.norc.org.
