Last month I wrote about the kind of cancers for which adults of a certain age should consider regular screening examinations. As part of that discussion I mentioned several forms of cancer for which there is no evidence of benefit from screening, and even some for which there is evidence of harm from screening! This is often challenging concept for patients and providers. For many years the common wisdom has been that all screening is good and more screening is better. But that approach has, in fact, been harmful in some instances. So let’s take a little closer look at two cancers that fit into this category.
Skin Cancer – It has traditionally been dogmatic that as part of an annual exam a thorough skin exam should be done to screen for skin cancer. However, there is not evidence that regular full skin exams are useful in preventing or impacting serious skin cancers. However, that is a different question than having people be aware of what a skin cancer may look like so that they can seek attention if they have concerning signs. The most useful criteria are for melanoma, known as the “ABCDEs”.
- A = Asymmetry – if the two halves of a mole do not match each other
- B = Border – if the borders of a mole are irregular, scalloped or notched
- C = Color – if there is more than one color to a mole
- D = Diameter – a mole more than ¼ inch (6mm), which is the size of a pencil eraser
- E = Evolving – a mole that is changing in shape, size or color over time.
It’s very important to note that these ABCDE characteristics do not mean that a mole is cancer. In fact, a common benign mole called seborrheic keratosis can often meet all 5 of these criteria. But the presence of one or more of these traits warrants a discussion with your health care provider.
Prostate Cancer – The PSA test is the poster child for harmful screening interventions. Beginning in the early 1990s and for 20 year we screened aggressively for prostate cancer in this country, recommending an annual PSA blood test starting at age 50 (often younger if there was a family history) with biopsies if the test was elevated. The result was a massive increase in the number of biopsies performed and an equally massive increase in the amount of prostate cancer being diagnosed. This resulted in surgery (removal of the prostate), radiation therapy and other treatments, with all of the myriad side effects, the most important of which are incontinence and impotence in treated men. In addition, the powerful emotional impact of telling someone that they have cancer takes a significant toll. The result of all of this diagnosis and treatment was zero impact on outcome – no improvement in survival from prostate cancer. The reason for this is that prostate cancer cells, though often present in the prostate as men age, most often do not behave like cancer as we think of it. The immune system may keep them under control for life or, once the disease causes symptoms, it is very treatable most of the time. In a minority of cases prostate cancer is aggressive and fatal, and unfortunately, diagnosing these cases earlier has not led to improved outcomes. There may someday be an effective screening test for prostate cancer, but the PSA is not that test and the strong recommendation right now is that men not undergo screening, even if there is a family history of prostate cancer. And by the way, having a rectal exam also has no impact on finding and changing the course of prostate cancer (or colon cancer ofr that matter) – so it’s OK to “just say no”!
There are some very aggressive cancers with typically poor prognoses, like ovarian and pancreatic cancer, for which no effective screening test has been identified. Women often feel that having an annual pelvic exam is part of ovarian cancer screening, but that is not effective. And as I said last month, there is new evidence in the last several years that has caused the United States Preventive Services Task Force to begin the process for evaluating recommendations for screening thyroid cancer.