Screening can lead to false positive as well as false negative results.
A false positive result means showing that cancer is present although it is actually not there. Such a result will cause patient anxiety and lead to more invasive procedures and tests.
A false negative result means showing that cancer is not present although it is actually present. This leads to delay in diagnosis and the patient will not seek the required medical care. My doctor has advised me to undergo a screening test for cancer.
Does this mean that he suspects that I have cancer?
Your doctor will advise screening test for cancer when you have some related symptoms or when you are in the age group that has a high risk for cancer development.
Are screening tests used to diagnose cancer?
Screening tests do not diagnose cancer. If the test result is positive, more tests will be required to establish diagnosis. If you had cancer in the past and if your parents &/or siblings have/had cancer, you have a higher risk of developing cancer and it may recommended by your doctor that you undergo screening tests to rule out/detect cancer.
Mammography is done to detect breast cancer. Breast MRI is done in women who have high risk of developing breast cancer. Women must also do self examination of the breasts regularly.
Low dose helical computed tomography has been used to detect lung cancer.
Colonoscopy/ Sigmoidoscopy have been used to detect colorectal cancer.
Pap smear test and human papilloma virus testing is used to detect cervical cancer.
Alpha-fetoprotein blood test is done in those who have high risk of developing liver cancer.
CA 125 test is done in women who have high risk of developing ovarian cancer.
Prostate specific antigen test is done to detect prostate cancer at an early stage. A weak elderly person should ideally not be screened for cancer. Even if the tests are positive, treatment will only harm the patient.