Here's Why Cancer Screenings Only Detect 14% of Cancers, and Why You Should Still Get Them

Cancer screenings are an important part of disease detection and treatment, but only 14% of all diagnosed cancers in the United States are detected through a preventative screening test, according to new research.

Using national health data, researchers at NORC at the University of Chicago developed a method to calculate how often cancers are detected via screening called “the percent of cancers detected by screening,” or PCDS. The team estimated PCDS by looking at U.S. data from several sources including the National Cancer Institute, self-reported preventive screening data from the National Health Information Survey, literature on screening test efficacy and state cancer statistics.

They found that only 14% of cancers in the U.S. are diagnosed after the patient had a recommended screening test, whereas the vast majority of cancers are found when symptoms appear or during other medical care.

Jennifer R. Jorgensen, MD, an assistant professor of obstetrics and gynecology at the University of Connecticut who was not involved in the research, told Verywell that she isn’t shocked by the findings given how low some cancer screening rates are. 

“The actual screening rates for these cancers in each of the states are not nearly as high as they should be,” Jorgensen said. “So it’s not surprising that only 14%, according to this study, are diagnosed with the screening tools.”

Since the data used in the study—which has not yet been peer-reviewed—is from 2017, it is likely that screening rates today are even lower. Other research has found that the pandemic has led to delayed or missed cancer screening appointments.

According to Jorgensen, screenings are important to detect early-stage cancer or pre-cancerous cells, echoing the report’s conclusion that improved screenings have the potential to detect cancers earlier and therefore lead to improved health outcomes. In the meantime, an important first step toward detecting more cancer is encouraging more people to get the screenings that do exist.

Which Cancers Have Recommended Screenings? And How Well Do They Work?

Currently, there are four types of cancers that have recommended screenings from the U.S. Preventive Services Task Force (USPSTF): breast, cervical, colorectal (or colon) and lung cancers. The NORC report says that as of 2017, these four cancers made up 29% of all cancer cases and 25% of all cancer deaths in the U.S.

The study researchers found that the percent of cancers detected via screening varies depending on the type of cancer: 61% of breast cancers; 52% of cervical cancers; 45% of colon cancers; and 3% of lung cancers.

While prostate cancer screening is not widely recommended by USPSTF, the report included data on it. It showed that 77% of prostate cancers were spotted by the relevant cancer screening.

The fact that only a handful of cancers have a recommended screening test means that about 57% of all diagnosed cancers currently do not have a recommended screening test, according to NORC’s estimate. The research team reports that these diseases are typically found in patients with later-stage cancers that are more difficult to treat. In total, these diagnoses account for 70% of cancer-related deaths, NORC says.

The fact that so many cancers do not have a recommended test is also likely a contributing factor to why only 14% of cancers are detected through screenings, Dana Scott, MD, an assistant professor of obstetrics and gynecology at the University of Connecticut who specializes in breast cancer, told Verywell. 

“There’s a lot of cancers that we don’t routinely screen for… [often because] they’re rare enough,” Scott said. “Those cancers are cancers that we don’t have a screening test for, or a good diagnostic screening test for.”

What Happens at a Cancer Screening?

Screenings for the four types of cancers that currently have screening recommendations in place vary in process.

Breast cancer: Mammograms are recommended for early detection often starting at age 45 to 50, though some may choose to start at about 40. Scott says that for people at higher risk of developing breast cancer, like those with a family history or those who carry a gene mutation that increases risk, additional screenings or assessments may be necessary.

“An important part of breast cancer screening is that risk assessment,” Scott said.

Cervical cancer: A Pap test, or Pap smear, is used to screen for cervical cancer. The test relies on a vaginal swab to collect cells from the cervix. Any abnormal cervical cells could turn into cancer. Jorgensen says cervical cancer screenings are very effective at detecting abnormal cells. 

Starting at age 21, women should get a Pap smear every three years, whereas women aged 30 to 65 should have a Pap test and an HPV test every five years, as recommended by American College of Obstetricians and Gynecologists (ACOG).

“About 70 to 80% of cervical cancers are usually caused by HPV,” Jorgensen said.

Colon cancer: Different test can be used to screen for colon cancer, including stool tests and colonoscopies. The American Cancer Society recommends that people at average risk of colon cancer start getting colonoscopies at the age of 45. While factors including family history and personal health risk can affect frequency, it is recommended that people get a colonoscopy every 10 years.

Lung cancer: The USPSTF recommends a yearly lung cancer screening with low-dose computed tomography (LDCT) for patients between the ages of 50 and 80 years with a history of heavy smoking.

How to Improve Cancer Detection

Both Scott and Jorgensen say that regular check-ups with your doctor and following through on cancer screenings is important. Some populations face greater barriers to health care, like those who are marginalized or do not have access to a family doctor, or recently lost their health insurance, which makes improving accessibility that much more critical.

Education also plays a role. Knowing your family history and personal risk factors can also help ensure you are getting the right screenings—and when. If you have a history of smoking, for example, your lung cancer screening might involve a different timeline than someone who has never smoked.

“A big key component is to make people aware of what risk factors might make them qualify for additional screening or qualify for earlier screening,” Scott said. “Patients might be going for screening, but not really getting the appropriate screening that they should be getting.”

Improving access to care and making it as easy as possible for patients to seek cancer screenings is also an important part of the equation.

“At UConn Health, patients can now self-schedule their mammogram so they don’t need a physician’s order, which I think helps with access,” Scott said.

Experts say adherence rates can always improve. With more education, patients can better understand how often to go for their cancer screenings—which often leads to better health outcomes.