Many types of cancer cause no noticeable symptoms. Others are much easier to beat when you catch them before you have a sign. That’s why regular screenings, which can reveal a potentially cancerous abnormality early on, are so important. So what cancers should you get screened for routinely, and how? And what if that screening reveals something isn’t right? We’ve got you covered. Here’s all you need to know about testing for cancer, from the whys to the when.
We went to some of the nation's top experts in cancer to bring you the most up-to-date information possible.
Stephen Edge, M.D.Surgical Oncologist and Vice President
Geoffrey Oxnard, M.D.Medical Oncologist
Daniel Y. Wang, M.D.Medical Oncologist, Assistant Professor of Medicine, Medical Oncology
What Is Cancer, Technically Speaking? Let’s Recap!
Before delving into the details of cancer screenings, let’s get clear on what the disease is: Cancer develops when abnormal cells grow out of control, due to mutations in our cells’ DNA. While normal cells that divide, get older and die, in a programmatic way, copying DNA as they go, cancer cells are renegades. They don’t stop growing when they should, and they never die. Instead, they mutate, replicate and form tumors. In blood cancers, like leukemia, they form a rebel army, amassing where they shouldn’t be.
Important distinction: A cell that’s abnormal isn’t necessarily cancerous. It could be benign (not cancer), or precancerous or premalignant (likely to become cancer). If it’s malignant, it’s already cancer. This is where screening and testing comes in: They enable doctors to investigate to determine what you’re dealing with.
Cancer cells can start growing pretty much anywhere in the body. And cancer is a label given to a collection of related diseases, which is why treatment ranges so vastly from, say, breast cancer to lymphoma. The spot where these cells start growing—called the primary site of your cancer—determines the type of cancer you have. When those cancer cells spread through your blood or lymphatic system (the network of tissues and organs that flush out toxins, waste, and all sorts of undesirables), the areas they invade are called metastatic sites.
While an annual physical exam is key for your doctor to monitor changes in your overall health, including organ and system function, there isn’t one comprehensive blood test (yet) available for cancer screening. Unless you have specific signs and symptoms of cancer, your primary care doctor will likely run panels to test your blood and body for many things, but not for cancer.
That’s why it’s important to stay on top of the recommended screening tests—mammogram, colonoscopy, Pap smear, for instance—for cancers you may be at risk for. A screening is a routine test done for patients without symptoms. If a screening reveals a possible abnormality, or if you have a sign or symptom of cancer, further testing to investigate, known as a diagnostic test, may be done.
Routine cancer screenings can catch the disease before it’s even progressed to the point where you have symptoms, leading to less invasive treatment and best outcomes. Case in point: between 1990 and 2015, the mortality rate for cancer dropped by 25%, and even more for commonly screened cancer types, like colorectal (47% for men and 44% for women) and breast cancer (39% for women). A good percentage of those numbers can be directly correlated with the introduction of screening for those cancer types, according to a 2017 article published in Seminars in Oncology Nursing.
What Screening Tests are Available for Cancer?
Of the 120+ types of cancer, only a handful are regularly screened for, meaning there are set guidelines for when and who should have them, issued by the American Cancer Society (ACS) and U.S. Preventive Services Task Force (USPSTF). The following are recommended:
What it is: Mammogram (an X-ray of the breast to look for early signs of breast cancer)
When to have it:
Women ages 40 to 44: can choose to start annual mammograms, covered by insurance
Women ages 45 to 54: should get mammograms every year
Women ages 55 and older: should get mammograms every 2 years
Good to know: Talk to your healthcare professional about the best breast screening plan for you. Regular screening should continue for as long as a woman is in good health and expects to live at least 10 more years. When breast cancer is found with mammography before a noticeable lump develops, it’s usually:
Less likely to have metastasized
More likely to be treated with surgery that can save more of a breast (56% vs 32%)
Less likely to receive chemotherapy (28% vs 56%)
Cervical Cancer Screening
What it is: Pap test (also called a Pap smear, a test on a sample of cells from the cervix to check for abnormalities)
When to have it:
Women ages 21 to 29: Pap test every 3 years
Women ages 30 to 65: Pap test and an HPV test (called co-testing) every 5 years, or a Pap test alone every 3 years
Women over age 65 who’ve had regular screening tests with normal results: no continued screening needed.
Good to know: Pap tests aren’t new, but they’re certainly effective. Mortality decreased by 80% for cervical cancer after the introduction of the Pap smear (invented by Greek immigrant George Papanicolau in 1929), a researcher reports in Surgical Clinics of North America. You might need to be tested more often because of your family history and other factors—talk to your doctor. A woman who has had a total hysterectomy (removal of the uterus and cervix) for reasons unrelated to cervical cancer should not be tested. Women who have been vaccinated against HPV should still follow screening recommendations for their age group.
How it’s done: Through colonoscopy (a flexible fiber-optic instrument is inserted through the anus to examine the colon for polyps, grows that can turn into cancer) Other times of colorectal screenings include:
Fecal occult blood test (FOBT)
Stool DNA testing
Double-contrast barium enema
When to have it:
Men and women ages 45 to 75: colonoscopy every 10 years
Men and women ages 76 to 86: discuss with your healthcare provider
Men and women over age 85: no continued screening needed
Good to know: Colonoscopies find at least 25% of polyps in men and women over the age of 50. And FOBT screenings every 2 years have been found to reduce colorectal cancers by 15%. Talk with your healthcare provider about your risk for colorectal cancer and which tests might be good for you, and talk to your insurance provider about your coverage. All abnormal results on non-colonoscopy screening tests (such as a stool-based test) should be followed up with a colonoscopy. Those at high risk for colorectal cancer because of family and/or personal history or other factors may need to:
What it is:low-dose CT scan (LDCT) (an X-ray screening of your lungs)
Who should get it: Those at higher risk of lung cancer because they are:
Ages 55 to 74 and in good health AND…
Smoke now or quit within the last 15 years AND…
Have smoked a pack a day for 30 years OR 2 packs per day for 15 years
Good to know: Screening should be discontinued once a person has not smoked for 15 years or has a health issue that limits life expectancy or the ability to have curative lung surgery.
Prostate Cancer Screening
What it is:Digital rectal examination (DRE) (doctor inserts a gloved, lubricated finger into your rectum to check the back wall of the prostate gland for enlargement) or a blood test called prostate specific antigen (PSA).
Who should get it: The ACS recommends that men make an informed decision with a healthcare provider about whether to be screened through either method, after discussing the risks and benefits with their doctor.
African American men and men with a father or brother who had prostate cancer before age 65 should discuss screening with their doctor starting at age 45.
Good to know: If you decide to be tested, it’s important to get a PSA blood test with or without a rectal exam. How often you’re tested will depend on your PSA level.
What Are the Issues With Cancer Screening?
Some cancer screening tests have risks—a colonoscopy, for instance, comes with the rare risk of bleeding from where a tissue sample was taken or a polyp was removed. There’s the possibility of a tear in the colon or rectum wall, called a perforation.
In any screening test, you can have a false-positive, meaning it says you have cancer, but on further testing, you actually don’t. There’s also the chance of a false-negative, when the test shows you don’t have cancer, but you do.
False-positive tests can lead to unnecessary stress, further testing, and overdiagnosis, while false-negative tests can delay early treatment. Since false positives and false negatives can happen with any screening, it’s important to know how likely one is to occur, and that is measured by sensitivity and specificity.
Sensitivity is the true positive rate—the closer the sensitivity is to 100%, the more likely it is you have the cancer type you’re being screened for.
Specificity is the opposite, the true negative rate—the closer the specificity is to 100%, the more likely you don’t have that specific cancer.
Digital mammography, for example, has a sensitivity of 97%, a specificity of 64.5% and diagnostic accuracy of 89.3%. A colonoscopy has a sensitivity of 92.5% and a specificity of 72.3%.
What Are Common Diagnostic Tests for Cancer
How do you know if you have cancer? If you’ve had a positive screening test, or you’ve had a symptom of cancer, or you have a significant family history of the cancer or a genetic factor like a known genetic mutation, your doctor will order a diagnostic test to investigate further. You’ll often receive results in 2-4 days, though it sometimes takes longer.
An exhaustive number of tests can be used for cancer. Here are some of the most common:
Physical Exam and History
Your doctor will examine you physically, checking for any abnormalities, lumps, anything out of the ordinary. He or she will also review your lifestyle, illnesses, and past treatments.
Biopsies remain one of the most common ways that doctors diagnose cancer. A doctor removes potentially cancerous tissue, typically from a mass or lump. It’s removed by:
Needle: Commonly used in for bone marrow aspirations, spinal taps, and some breast, prostate, and liver biopsies
Endoscopy: A tube-like instrument that can see inside your organs, used for:
Bronchoscopy (bronchi, main pathways to the lungs)
Cystoscopy (bladder and urethra)
Laparoscopy (abdominal wall)
Laryngoscopy (larynx and throat)
Mediastinoscopy (mediastinum, the space between your lungs)
Thoracoscopy (surface and lining of the lungs)
Upper Endoscopy (upper digestive tract, including esophagus, stomach and first part of small intestine)
A pathologist then examines the tissue under a microscope and runs tests to determine if it’s cancer. Based on those findings, your doctor will receive a pathologist report, a diagnostic document that will help determine your cancer stage and treatment.
Bodily Fluid Tests
Bodily fluids like urine and blood, can be tested for cancer using tumor marker tests. Tumor markers are substances made by cancer cells or normal cells in response to cancer and they’re found in blood, urine and body tissues.
Urine, for instance, can be used to detect and diagnose kidney, urothelial, bladder, and other cancers. Unfortunately, there isn’t one blood test that can find all cancer types, though one is under investigation that could detect 20+ different cancers, at varying stages, in the blood using next-generation sequencing technology.
The following blood tests are now used to detect specific cancer types:
The PSA test is used to detect prostate cancer. While it helps detect cancer, there’s no way to know if that cancer would have advanced enough in a man’s lifetime to cause harm.
The CA-125 blood test (often done in concert with a transvaginal ultrasound) can detect ovarian cancer in women with symptoms or who’ve had the cancer type before.
The alpha-fetoprotein blood test (often done with an ultrasound of the liver) could help find liver cancer early on in high-risk patients.
Imaging (Radiology Tests)
These tests, which take photos of your insides, can help your doctor determine the type of cancer and its spread, as well as whether your treatment is working. They include:
Computed tomography (CT) scan
Magnetic Resonance Imaging (MRI)
X-rays and other radiographic test
Nuclear medicine scan
If screenings and testing seems like a lot to stay on top of, that’s because it is! Remember, your doctor is your partner in making sure you get the recommended screenings you need. Keep your appointments, don’t wait to do the necessary follow-ups, and definitely reach out if you notice anything weird between appointments. Proper screening paired with self-awareness can help catch cancer early, and treat it effectively.
Frequently Asked QuestionsCancer Tests
Is there a blood test for cancer?
Here’s the thing. This question can be answered with both a yes and a no. Blood tests like the complete blood count test, which measures the amount of blood cells in your sample, can detect cancers of the blood. If you don’t have enough of certain blood cell types—or you have too many—doctors can detect if you might have a blood cancer (a bone marrow biopsy can help confirm that diagnosis). But no one blood test can detect all forms of cancer--yet. However, blood tests can determine how well your organs are functioning, which can indicate inflammation or other cancer-related concerns that need investigation. Other blood tests, like tumor marker tests, can find chemicals made by tumors in your blood, but those chemicals can be produced by non-cancerous cells too, so this test isn’t optimal for testing and diagnosis.
How do doctors test for pancreatic cancer?
Your doctor may have you undergo an imaging test, such as an ultrasound or CT scan, to take digital photos of your internal organs, including the pancreas. You might have an endoscopic ultrasound, where an ultrasound device is passed through an endoscope, a thin tube, into your esophagus and stomach, to take images of your pancreas. You might have a biopsy, too, often as part of the endoscopic ultrasound or during what’s called a fine-needle aspiration, to remove a tissue sample from your pancreas. You have your blood drawn to test for a specific tumor marker, CA19-9, that might be elevated in pancreatic cancer. However, not everyone with pancreatic cancer has elevated tumor markers.
What is a CRP blood test?
The C-reactive protein blood test, known by its acronym CRP, detects inflammation, caused by infection and trauma, in your body. Your doctor can use this blood test to determine a range of potential issues that need investigating, including the possibility of cancer. Increased levels of inflammation have been linked to cancers including liver, colorectal, lung, and gastric. Because the test is generic in a sense—it finds overall inflammation in the body, your doctor can't point to elevated results from this test and say, definitively, that you have one cancer type or another. More tests will be needed.
Can you test for colon cancer without a colonoscopy?
Yes! While colonoscopies are the most common screening test for colorectal cancer in the U.S., with many benefits (including excellent early detection), they also require some prep and assistance driving home after the sedation needed for the procedure. Alternatives to a colonoscopy include fecal immunochemical tests (FIT), a stool DNA test (sDNA), high-sensitivity fecal occult blood tests (FOBT), a flexible sigmoidoscopy, and virtual colonoscopy (sometimes called a CT colonography).