Monitoring Disease: What Cells Tell Us

As scientific understanding of cancer deepened and as treatment options expanded, the medical context of cancer care shifted to an emphasis on early detection and aggressive treatment. Imaging techniques were refined to spot ever tinier tumors, researchers developed biomarkers that reflected physiological changes produced by cancer in the early stages, and the link was made to certain viral infections, such as Human Papilloma Virus (HPV) that greatly increased the risk of cervical cancer years later. We entered the era of cancer screening.

The basis of cancer screening is that many types of cancer can be found before they cause symptoms. As the National Cancer Institute (NCI) describes it, “Screening can help doctors find and treat some types of cancer early. Generally, cancer treatment is more effective when the disease is found early. However, not all types of cancer have screening tests and some tests are only for people with specific genetic risks.” The hope is that earlier and more accurate diagnostic information will keep moving cancer survival rates higher and longer.

There are different kinds of screening tests. Screening for cancer begins with the physical exam, checking for lumps or anything otherwise unusual. Both the patient’s personal medical history as well as family medical history will also provide information that puts the individual’s cancer risk into larger context. Laboratory tests are also often involved, which can include blood samples, as well as biopsies. And for some cancers, there are also genetic tests that look for certain gene mutations that are linked to increased cancer risk.

Right now, we tend to associate different cancers with different diagnostic tests, for example, lung cancer with imaging, prostate cancer with a blood test and breast cancer with a genetic test. Increasingly, however, all types of screening tests are being brought to bear on cancers, and that is a trend that is expected to continue in the future. The combined results of blood tests, imaging scans, and genetic tests will help narrow the diagnosis and focus the treatment, opening up new opportunities, as well as new challenges in cancer care. LESS

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The critics of universal screening are not medical anti-interventionists. In fact, even the NCI acknowledges, “Not all screening tests are helpful and most have risks. It is important to know the risks of the test and whether it has been proven to decrease the chance of dying from cancer. Some screening tests cause serious problems.”

Those problems can include complications accompanying a test, such as a tear in the lining of the colon from a colonoscopy, or damage to the esophagus from an endoscopy. But they can also include less obvious problems, such as erroneous test results that show there is cancer when there really isn’t (called a false positive), which triggers anxiety and follow-up testing, or test results that indicate all is normal when there is actually cancer (called a false negative), which offer a sense of security that may end up delaying treatment until symptoms are obvious.

Full-body CT (computerized tomography) scans, which have become popular in recent years, expose patients to high levels of radiation that may itself cause cancers later in a certain small fraction of individuals. Probably more likely, however, is that full body scans uncover a host of abnormalities that are likely to never cause further problems, but once uncovered become tough to ignore and tough to not treat.

Perfect testing would avoid those problems, but even the best current tests cannot avoid false positives and false negatives, and many tests have alarmingly high rates of such mistaken results. And finally, and perhaps most troublesome, is the fact that finding the cancer may not actually improve the patient’s health or help the patient live longer.

Some cancers never become life threatening, but if they are found by a screening test, they are usually treated. For many cancers there is little or no chance of survival without treatment. But in other cases there is just no way to know if treatment will help a person live longer. Cancer treatments are notorious for having serious side effects that can damage or destroy a patient’s quality of life. Moreover, with some cancers, treating the disease early makes virtually no difference in outcome than waiting to treat it later.

Not all cancers and not all screening tests are equal. And that can make it very difficult to make informed decisions about screening. As the NCI advises, screening tests have many goals and those that are most helpful do the following:

• Finds cancer before symptoms appear.


• Screens for a cancer that is easier to treat and cure when found early.


• Have few false-negative test results and false-positive test results.


• Decreases the chance of dying from cancer.

It is also important to keep in mind that screening tests usually do not diagnose cancer. If a screening test result is abnormal, more tests, such as biopsies, are typically done to confirm that it is or isn’t cancer. LESS

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In order to determine whether a screening test is beneficial, we need to be ask the question, according the Mayo Clinic, “Do early detection and early treatment improve treatment outcomes and decrease the number of deaths from prostate cancer? Two recent large studies have produced somewhat competing answers, leading many experts to argue that there isn't enough evidence to answer this question.”

A major consideration in answering this question is the typical course of prostate cancer. “If,” as the Mayo Clinic poses the issue, “all cases of prostate cancer progressed rapidly and caused poor health and death, then early detection would clearly be a good thing. However, prostate cancer usually progresses slowly over many years, and the majority of cases are diagnosed in men over the age of 65. Therefore, a man may have prostate cancer that never causes symptoms or never becomes a medical problem.”

In fact, some researchers believe that 100% of men will develop prostate cancer if they live long enough. That’s a big if, however. Most men will die of something else before that time. So should all men eventually be treated for prostate cancer? No one would suggest that. In fact, according to the Mayo Clinic, “studies have estimated that between 29 and 44 percent of men with prostate cancer detected by PSA tests have tumors that wouldn't result in symptoms during their lifetimes.” LESS

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