What the results mean

Test results must be interpreted carefully because several factors can influence test outcomes, such as variations in your body or even what you eat.

In addition, keep in mind that noncancerous conditions can sometimes cause abnormal test results. And, in other cases, cancer may be present even though the blood test results are normal.

Your doctor reviews your test results to determine whether your levels fall within a normal range. Or your doctor may compare your results with those from past tests.

What happens next

Though blood and urine tests can help give your doctor clues, other tests are usually necessary to make the diagnosis. For most forms of cancer, a biopsy — a procedure to obtain a sample of suspicious cells for testing — is usually necessary to make a definitive diagnosis.

In some cases, tumor marker levels are monitored over time. Your doctor may schedule follow-up testing in a few months. Tumor markers are most often helpful after your cancer diagnosis. Your doctor may use these tests to determine whether your cancer is responding to treatment or whether your cancer is growing.

In most cases, after you complete your cancer treatment, using cancer blood tests isn't helpful for watching for a return of the cancer. Discuss the specifics of your cancer with your doctor.

Nov. 22, 2016 See more In-depth