Cancer screening comprises tests that detect cancer, or conditions that may evolve into cancer, before symptoms appear.
According to the National Cancer Institute, cancer screening reduces the risk of dying of certain cancers and increases the chance of successful treatment in many cancers. Detecting a cancer in the earlier stages often means the cancer has not spread (metastasized) and will be easier to treat than if it had spread.
A cancer diagnosis follows a positive cancer screening. The oncologist’s diagnosis includes staging (the process of determining how advanced the cancer is), where the cancer is located and whether it has begun to spread.
A number of cancer screening tests are available and vary according to the type of cancer screened for. Screening may include a physical exam, blood tests, biopsies, imaging procedures and genetic testing.
The most common cancer screening tests include the following.
Colonoscopy
During this physical exam that tests for colorectal cancer, a doctor examines the inner lining of the colon and rectum (large intestine) to check for precancerous and cancerous cells using a colonoscope (a flexible, thin tube).
During a colonoscopy, a doctor collects tissue to biopsy and check for abnormalities or remove irregular growths throughout the inner lining of the large intestine.
Mammography
An imaging exam that screens for breast cancer, a mammography uses low-dose X-rays to look for cancer cells in the breast tissue.
Low-dose helical computed tomography
This form of CT scan exam screens for lung cancer. A patient lies horizontally while the machine scans the patient’s torso by rotating in a spiral motion around the torso.
Pap and HPV testing
A pap test screens for cervical cancer and an HPV screens for the human papillomavirus, which can lead to cervical cancer. These tests can detect precancerous cells so that preventive procedures can treat the cells before cancer begins to grow.
Pap and HPV screening is performed by taking a sample of uterine cells in an office and sending it to a lab.
PSA test
The prostate-specific antigen (PSA) is a lab test that indicates the possible presence of prostate cancer from a man’s blood sample. The test is carried out by measuring the level of PSA, which is the protein that malignant and benign prostate cancer produces.
Cancer is diagnosed by a combination of physical exam, screening methods mentioned above and diagnostic tests. Following a positive result from cancer screening, an oncologist will diagnose the type of cancer. An accurate diagnosis is necessary to determine a proper course of treatment.
A cancer diagnosis varies by the type of cancer, the staging and whether the tumor has moved to other parts of the body (metastasized). General staging includes a scale from 0 to IV. Stage IV means that the cancer has spread to distant organs or body tissues, and stage 0 typically represents precancerous cells.
All cancers will be staged upon initial diagnosis. The stage will affect the initial treatment course. For example, earlier stage cancers can typically be treated solely with surgery to remove the cancerous or precancerous cells, while later stage cancers may require a combination of surgery, radiation chemotherapy or targeted therapies.
Although cancer screening saves lives every year, there are some limitations and risks to consider. The possibility of both false-positive and false-negative results is a major consideration of cancer screening, as the tests are not flawless.
Patients should consider the following.