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 But that doesn’t mean we shouldn’t use sunscreen, doctors say. It
just means it’s unethical to do experiments testing the
effectiveness of sunscreen by randomly assigning some people to use
it and others to skip it.
“Lack of high quality experimental evidence should not be equated
with evidence that such interventions are ineffective and it is
important that patients and consumers do not stop protecting their
skin until better quality evidence emerges,” lead authors Dr. Ingrid
Arevalo-Rodriguez and Dr. Guillermo Sanchez of the Instituto de
Evaluacion Technoloica en Salud in Bogota, Colombia told Reuters
Health by email.
Dr. Laura Ferris, a dermatologist at the University of Pittsburgh
who wasn’t involved in the research review, pointed out, also by
email, that it’s difficult to measure the effect of sun protection
on the prevention of skin cancer, “particularly because it is not
ethical or practical to randomize the population.”
“One could not, for example, tell one group to seek shade, wear a
hat, and use sunscreen and another to sit in the direct sun and
abstain from use of sunscreen,” Ferris added. “So lack of evidence
does not mean that sun protection has no impact on the risk of skin
cancer, just that the impact is difficult to measure.”
In a review published by the Cochrane Library, Arevalo-Rodriguez and
Sanchez and colleagues set out to assess how much we already know
about whether sunscreen and other protective measures, such as
wearing hats or sunglasses or staying in the shade, prevent skin
cancer.
They focused on what’s known as basal cell and cutaneous squamous
cell carcinomas, which make up the majority of skin cancer cases.
Their analysis didn’t look at melanoma, a rare and much more deadly
type of skin cancer.
The research team only wanted to look at trials that randomly
assigned some people to use sunscreen or other protection - and they
found just one study that met their criteria.
This study, done in Australia, monitored about 1,600 people for more
than four years and didn’t find a meaningful difference in the
number of new cancer cases detected based on whether people used
sunscreen every day or only occasionally.
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That might not be long enough to follow patients to see if sunscreen
prevents skin cancer because it can take several years after sun
exposure to detect abnormalities on the skin.
What this does suggest is that more high-quality research is needed,
the authors told Reuters Health.
In the meantime, “Patients and consumers in general need to consult
health professionals to obtain specific advice about the need of
specific preventive measures, according with their age, skin color,
occupation and presence of other risk factors for skin cancer, among
other factors,” they added.
Even without more studies, there’s already plenty of proof that
exposure to ultraviolet rays from the sun causes skin cancer and
melanoma, noted Dr. David Leffell, a skin cancer researcher at Yale
School of Medicine who wasn’t involved in the research review.
“The scientific facts are inescapable—regular use of sun protection
reduces skin cancer and cancer precursors,” Leffell said by email.
“The benefits of sun protection and the incontrovertible evidence of
sunburn and chronic sun exposure as a cause of about 60% of
melanomas should inspire people to continue reasonable sun
protection if they fit into the moderate to high risk groups, and
even if they don’t,” Leffell added.
SOURCE: http://bit.ly/2aDI7kF Cochrane Library, online July 25,
2016.
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