Cancer is a major contributor to illness and mortality worldwide (1). However, catching cancer early can increase the chance of successfully treating it. One strategy for early diagnosis is screening. The purpose of screening is to detect abnormalities that point to the potential presence of cancer or pre-cancer prior to the individual starting to experience symptoms (1). Sounds optimal, right? The answer is yes, but only for some. As with many things in life, there is no “one-size-fits-all” model when it comes to screening. The decision of whether to screen or not to screen depends on weighing the benefits and harms for individuals or groups (2-5). But what does the research have to say about different forms of cancer screening? Here are just a few of the evidence-based insights on screening for prostate cancer, ovarian cancer, and breast cancer. Click on the links below to learn more.
Prostate-specific antigen (PSA) is a protein produced by the prostate cells. The PSA test is used to assess the level of PSA in the blood, with high levels of PSA eluding to the potential presence of prostate cancer. Despite the wide-use of this test as a method for prostate cancer screening, it is not deemed very reliable, and the Canadian Preventive Taskforce does not recommend its use as a screening tool. In particular, the PSA test is not advised for use in men under 55 and over 70 years of age, while those aged 55 to 69 (the highest risk group) are directed to speak with a health professional about available screening options prior to opting for a PSA test. Why is that? Well, the benefits of the PSA test are not consistent, but the harms—including false positive results, complications associated with further tests undertaken to help reach a diagnosis (e.g., biopsies), and overdiagnosis—are noteworthy (2;3). These results relate to men who do not have symptoms of prostate cancer prior to screening. It is also important to mention that recommendations around using or not using PSA tests are not agreed upon by all experts (6).
Transvaginal ultrasounds and/or cancer antigen 125 (CA-125) blood tests are two methods used to screen for ovarian cancer (4;7). The ultrasound takes images of the ovaries, while the blood test looks for high levels of the CA-125 protein. Research shows that ovarian cancer screening does not decrease deaths from ovarian cancer in women who are over the age of 45, symptomless, and at “average risk” of the disease. However, false positive test results have the potential to lead to unnecessary surgeries in this population (4). As such, both the US Preventive Services Task Force and the Canadian Preventive Taskforce do not recommend ovarian cancer screening in women with an “average risk” of ovarian cancer who do not have symptoms (4;7-8).
Mammography—or a mammogram—involves taking x-ray images of the breasts to screen for breast cancer (5;9-10). In women at “average risk” for breast cancer, mammography reduces the risk of death in those aged 50 to 69 years, but not in those under 50 years old and between 70 and 74 years old. With that said, the findings for the under 50 and between 70 and 74 age groups are not as conclusive. What’s more, mammography, may also increase the risk of overdiagnosis in women under 50 years of age, as well as those between 50 and 69 years of age (4). Similar to PSA tests, varying opinions exist around the use mammography, specifically on issues such as which groups should be screened and when to initiate screening (4;11-13).
Please note that the results for ovarian and breast cancer screening are only relevant to people at "average risk" of those cancers, and NOT high risk folks, while the results for prostate cancer screening are relevant to men without symptoms of prostate cancer.
Next to steps for you
You might be thinking, “What does this mean for me?” and no one would blame you. Between some inconclusive results, differing findings by age group, and mixed-messaging by experts, it can be hard to tease out what is best for you. The good news is you do not have to figure it all out on your own. Decisions around whether to screen, which screening option is best for you, and how to go about it should be made in consultation with your health care team. Together you can assess your level of risk, weigh the benefits and harms for you as an individual, and incorporate your preferences.