PracticalDermatology

Skin cancer prevention is the dermatology equivalent of general health advocacy in primary care. Rarely is UV protection the focus of our patient visits, but it is critical that we routinely prompt our patients about the importance of sun avoidance. To that effect, although UV protection is a multifaceted process, sunscreen may be the one product with which dermatologists are most associated. Whether we wrap our patient visits with friendly reminders to “always remember the sunscreen,” or we're fielding questions about which brands or SPF values to use, being prepared to give clear, concise information about sunscreen remains an essential part of our job as dermatologists.

New Research, New Questions

Over the last several years, much conjecture has surrounded the issue of SPF and what clinicians should recommend. When the FDA released its final rule and label changes for sunscreens, it ruled that sunscreen products with SPF of less than 15 could not be considered “broad spectrum.” (Note: The FDA's definition of “broad spectrum” is somewhat misleading, as it does not quantify UVA.) Thus, it would be natural for patients to think that SPF 15 was the “right” number. As any clinician knows, the reality is much more nuanced. While SPF 15 might be an acceptable minimum SPF to be considered broad spectrum by the FDA, new evidence suggests that SPF 30 may be a better recommendation.

In a study published earlier this year, researchers sought to estimate the expected frequency and magnitude of sunburn resulting from typical use of sunscreens labeled SPF 15 and SPF 30 “by people spending long periods outdoors in strong summer sunshine.”¹ They developed a simulation model by combining the probability distribution of the measured sun protection factor (SPF) in vivo with those for the average application thickness and the uniformity of application over the skin surface. The model estimated the variation in delivered protection over the exposed skin surface from consumer use of sunscreens.

The results showed that while either sunscreen would be sufficient to prevent any erythema, “the combination of the average quantity applied with the variability in thickness over the skin surface will lead to erythema, especially in SPF 15 sunscreen users,” the researchers noted. They concluded that those who intend to spend long periods outside in strong sunshine would be better advised to use suncreens with an SPF of 30 rather than SPF 15 sunscreens. Moreover, the researchers noted that clinicians should advise patients to apply the product carefully over exposed skin if they wish to minimize their risk of sunburn and, by implication, skin cancer.

The Higher the Better

These results suggest that SPF 30 might be a better recommendation when it comes to the minimum recommendation. Of course, the factors that impact UV exposure and skin cancer risk are more complex than a broad recommendation for an SPF value. Excluding any criticisms of the current model for SPF (which does not account for UVA), a host of other factors should be taken into account, such as duration of sun exposure and frequency of application. But in real life, we know that application is erratic at best. Moreover, we only command so much of our patients' attention when it comes to influencing their behaviors and the behavior of the public at large. That is why SPF matters. We can never know each patient's exact situation; how many hours they spend in the sun, whether their jobs entail incidental sun exposure; etc. Thus, while a one-size-fits-all recommendation will never address the complexity of skin cancer prevention, the number we generally recommend can make a difference, and SPF 30 therefore appears to be a safer recommendation.

Jonathan Wolfe, MD is a Clinical Associate Professor of Dermatology at the University of Pennsylvania in Philadelphia, PA, where he is on the staff of the Pigmented Lesion Clinic. He is also in private practice in Plymouth Meeting, PA.

1. Pissavini M, Diffey B. Photodermatol Photoimmunol Photomed. 2013;29(3):111-115.