The US Preventative Services Task Force (USPSTF) has released its latest update to the 2009 recommendations of skin cancer screenings. The verdict is that there currently isn’t enough evidence that screening adults for melanoma has any impact on skin cancer appearance or death among any adult group, even those who would be considered at-risk.
Quick Primer: Screening
Screening is the practice of checking a large population for a specific disease. The difference between screening and testing is that, while testing is usually done to confirm a suspected diagnoses, screening is carried out on people who aren’t showing symptoms or in some cases even risk factors. Screening is a matter of great contention in both the medical community and the public at large, as evidenced by the debate that erupts whenever the topic of breast cancer screening appears.
The USPSTF recommendations specifically concern skin cancer screening guidelines for a type of full-body skin inspection that is conducted visually by either a doctor or a dermatologist. During this screening, the inspector is looking for things like suspicious lesions, moles that might have grown or changed colour, or other indicators that a tumor may be present.
Risks of Screening
When deciding whether screening is worth recommending, several considerations have to be made. The first is the potential for unnecessary harm to patients. If something is discovered during a screen then it needs to be discovered, but usually by excising part of the lesion for a biopsy. There are several ways harm can result from this:
- The mental stress from the patient thinking they may have cancer
- Any cosmetic harm that treatments and tests may cause
- The inherent risk of the biopsy itself (no procedure is without some risk, however small)
- The potential for a false positive and the ensuing unnecessary treatment and confusion
- The potential for an overdiagnosis, which is when a cancer is found and removed that would not have caused problems if left alone (hard to quantify, but it does happen)
According to the USPSTF, there is enough evidence to conclude that visual screening does result in false positives, overdiagnosis, and both cosmetic and real harm, though the evidence isn’t clear enough to determine the exact frequency this happens.
Benefits of Screening
The above risks to any screening program are always weighed against the potential benefits of the process. These benefits can come from reducing actual occurrences of melanoma (by finding/removing lesions before they become cancerous) and reducing deaths from melanoma (by catching it early so treatment can have maximum effect). By looking at research that compares rates of melanoma incidence and deaths among screened and unscreened populations, the USPSTF sought to see whether there was any benefit.
The task force’s finding is that the evidence for benefit was limited. One of the studies suggested it would take around 4,000 excisions to prevent one death from melanoma. Another study found that screening would only prevent one fewer death for every 100,000 people screened during a single decade. As the USPSTF noted, there wasn’t enough evidence to recommend visual screening for even at-risk populations.
Skin cancer screenings can cause very real harm to patients in the form of misdiagnoses, overdiagnosis, and the inherent risks of biopsies and other procedures. The available evidence is not enough to suggest there are enough benefits to outweigh these risks, so screening cannot be recommended for adults regardless of whether they are at-risk or not. The USPSTF has also brought attention to the relatively limited nature of the available research on screening. Science is an ongoing process of refinement based on evidence, so if some of these gaps get filled in by researchers then the recommendations may change when next reviewed. For now, screening is only recommended for patients who have a personal history of skin cancer or who have potential symptoms such as a mole that is changing size, shape, or color.
“Screening for Skin Cancer US Preventive Services Task Force Recommendation Statement,” JAMA, 2016; 10.1001/jama.2016.8465.