According to the US Preventive Services Task Force (USPSTF), only limited evidence exists that skin cancer screening for adults is effective, particularly for melanoma mortality.
USPSTF evidence-based preventive care recommendations
Finding melanoma at early stages improves outcomes. That has led to research on the subject and suggestions from professional groups, such as the American Academy of Dermatology and the Skin Cancer Foundation, for yearly visits with a dermatologist.
The USPSTF is a group of independent preventive-care experts supported by the Agency for Healthcare Research and Quality.
“We come together to make evidence-based preventive care recommendations for clinical services, those provided or ordered within the clinical setting,” said task force member Michael Pignone, MD, PhD, professor of medicine at the Dell Medical School at the University of Texas at Austin.
Although the task force screens issues, it also makes—and regularly updates—recommendations in other areas of preventive medicine such as counseling and medications. The last update on skin cancer was published in 2009. In this case, the task force chose the Group Health Research Institute at Kaiser Permanente Research Affiliates Evidence-based Practice Center in Portland, OR, to do the research on skin cancer screening. The center assembled the research and reviewed the information. “The ability to find and treat melanoma with the most conservative surgery possible may be a benefit of screening,” Fundakowski said. “It may not have an impact on survival.”
The task force’s research plan on screening for skin cancer was posted for public comment in May. The final recommendation was released on 26 July 2016, about two years after the task force completed its work.
“We proposed a work with a set of questions that was posted publicly, and comments were received,” said coauthor Nora Henrikson, PhD, MPH, a research associate at the Group Health Research Institute in Seattle and a coinvestigator at the center. “After the task force and the Agency for Healthcare Research and Quality approve the work plan, we conduct the systematic review of the literature. Once we identify the articles that meet our inclusion criteria, we extract the data from each. That becomes the basis for our report”.
Once the task force reviewed the information, it was clear that the evidence for skin cancer screening wasn’t very strong.
“We found that there is really very limited information available to answer our questions,” Henrikson said.
Insufficient evidence to support recommendation
Therefore, the USPSTF issued an I statement, meaning insufficient evidence was present to support a recommendation either for or against the clinical service. The I is given when the evidence is nonexistent, unclear, or contradictory and when assessing the magnitudes of harm versus benefits isn’t possible.
That doesn’t mean skin cancer screening isn’t effective, however.
“Often when the task force issues an I statement, it is misconstrued as a recommendation against screening, and that is not the case,” Pignone said. “This is just an indication that we that we don’t know enough information to give good, evidence-based guidance.”
He said that patients and their doctors should decide about screening on the basis of each patient’s specific circumstances.
“A really important caveat in this is to remember that this is a discussion of screening an asymptomatic person of average risk,” Pignone said. “This doesn’t apply to those with a previous diagnosis of melanoma, who have a strong family history, or something that worries them. Their increased risk may warrant a different approach.”
Impediments to further research
The task force also issues suggestions for areas of research that are needed to provide more evidence for each service they assess. However, many of those recommended studies may be hard to perform given the relatively slow growth of the lesions and the few cases in comparison with other cancers.
“It would require a very large study to enroll enough people into a randomized, controlled trial of screening and then following them all the way out to skin cancer outcomes,” Henrikson said. “That may be a priority for funding compared to other kinds of screenings or preventive interventions.”
Another impediment to getting substantive research into screening for skin cancers is the way melanoma develops.
“If the goal of the screening program is to identify and treat patients as early as possible in order to increase survival, it may not be easy to demonstrate, as the five-year survival rate based on the Surveillance, Epidemiology, and End Results (SEER) Program database is already at 91%,” said Christopher Fundakowski, MD, assistant professor of surgical oncology at Fox Chase Cancer Center in Philadelphia. “This is largely because the majority of melanomas will present at localized or early stage.”
Morbidity of treatment
Although most patients with melanoma will be alive at five years, other factors must be considered, such as the morbidity and potential disfigurement caused by surgery. “The ability to find and treat melanoma with the most conservative surgery possible may be a benefit of screening,” Fundakowski said. “It may not have an impact on survival.”
Eye as an assessment tool
Another concern is that the difference between a slow-growing lesion and a more aggressive one can be just a few millimeters. Big differences occur with very small changes.
“When we are using the eye as an assessment tool, it just isn’t a fine enough instrument to detect these kinds of differences with any accuracy,” Fundakowski said. “That is why sensitivity of visual screening, or the ability to correctly identify melanoma, is around 50%.”
Most people with skin cancers do well. That trend makes developing a successful screening program difficult.
“When you have many more deaths, it is easier to create screening tests that save more people,” Fundakowski said. “For skin cancer, you would need very specialized screening methods, and we just don’t have them yet.”
The big win for melanoma patients will come when physicians can readily identify deep lesions and those likely to spread.
“While this is a small percentage of all melanomas, these are the patients who will have the most to gain from early diagnosis and treatment,” he said.
Featured image credit: Micrograph of malignant melanoma. Photo by Nephron. CC BY-SA 3.0 via Wikimedia Commons.