What Cancer Screening Can and Cannot Detect

This page is for anyone who wants to know which cancers screening can and cannot find. It also covers what to do about the gaps.

There are more than a hundred types of cancer. Screening tests recommended for average-risk adults exist for four of them. Prostate cancer makes a fifth, but it is handled as a shared decision rather than a routine test.

• Breast: mammography, generally from 40.
• Cervical: HPV testing and cytology (a Pap test, which checks cells under a microscope), from 21 to 65.
• Colorectal: colonoscopy, stool tests, sigmoidoscopy, or CT colonography, from 45 to 75.
• Lung: annual low-dose CT for people 50 to 80 who meet smoking-history criteria.
• Prostate: PSA, offered as an individual decision for men 55 to 69, not recommended at 70 and older.

Everything else falls outside routine screening.

For people at average risk, there is no recommended screening for pancreatic, ovarian, kidney, liver, stomach, esophageal, brain, uterine, bladder, testicular, or thyroid cancer. There is none for leukemias, lymphomas, myeloma, or sarcomas either. NCI's screening page lists recommended tests for only the five cancers above.

The reasons repeat. Some of these cancers are uncommon enough that even an accurate test would produce mostly false positives. Some sit in organs that are hard to image without expensive or invasive procedures. And for several, finding the cancer earlier has not been shown to change how the disease ends. These are general explanations, not NCI quotes.

High-risk surveillance is a separate matter. Some people have an inherited syndrome, chronic hepatitis B, cirrhosis, or Barrett esophagus. They may be monitored for cancers that have no general-population screening. In those groups the arithmetic is different.

These are worth knowing about, because they are still sometimes offered.

Ovarian cancer screening. CA-125 blood testing and transvaginal ultrasound were tested in the PLCO trial across nearly 69,000 women. There was no reduction in ovarian cancer deaths. Along the way 9.6 percent of screened women had a false-positive result. Of those screened, 3.17 percent underwent surgery because of it. And up to 15 percent of those surgeries produced a major complication. The USPSTF recommendation is a Grade D.

Breast self-exam and clinical breast exam. NCI says neither is an adequate breast cancer screening test on its own. Mammography is the test credited with reducing breast cancer deaths.

Skin examination. NCI says skin exams to screen for skin cancer have not been shown to decrease deaths from the disease.

Thyroid screening by neck exam or ultrasound. NCI says there is no standard or routine screening test for thyroid cancer. Neck exams and ultrasound do not lower the risk of dying from it. They can find cancers that may never cause symptoms (overdiagnosis), and treatment carries risks.

Blood tests that claim to detect many cancers at once are the most prominent current entrant. The honest status is unresolved. NCI states that whether these tests are effective for cancer screening in people without symptoms is unknown, and needs to be assessed through randomized clinical trials. NCI says no multi-cancer detection test has been approved by the FDA.

Two practical risks are worth naming before ordering one. First, a negative result may be read as an all-clear it cannot support. Someone might then skip a colonoscopy or a mammogram that does have proven benefit. Second, a positive result starts a search across the whole body. Sometimes that search ends without a located cancer, and without a way to close the question.

The interval. Screening is a snapshot. A normal result covers the day of the test, not the months after it.

Symptoms. Screening is for people without symptoms. Once you have a symptom, you have left screening and entered diagnosis. The two follow different rules. A recent normal mammogram is not a reason to wait on a new breast lump. A recent normal colonoscopy is not a reason to ignore rectal bleeding.

The most useful sentence to have ready is a short one: "I know my last screening was normal, but this is new, and I want it checked."

For the many cancers with no screening test, prevention carries more weight than detection ever could. NCI's prevention guidance includes checking the radon level in your home. Ask your care team which other steps fit your own risks. Prevention aims to lower the number of cancers that occur, rather than changing when they are found.

• NCI: Cancer Screening Overview (PDQ) - Patient Version
• USPSTF: Ovarian cancer screening recommendation
• NCI: Cancer Screening Tests
• NCI: Breast Cancer Screening (PDQ)
• NCI: Skin Cancer Screening (PDQ)
• NCI: Thyroid Cancer Screening (PDQ)
• USPSTF: Prostate cancer screening
• NCI: What cancer screening statistics really tell us
• NCI: Cancer prevention overview and risk factors