Environmental Solar Ultraviolet Exposure May Decrease Risk for Mycosis Fungoides

person reaching towards sun
person reaching towards sun

According to study data published in the Journal of the American Academy of Dermatology, environmental exposure to ultraviolet (UV) light may reduce the risk for mycosis fungoides.

Investigators used the Surveillance, Epidemiology, and End Results-18 (SEER-18) database to identify adult patients (age ≥20 years) with mycosis fungoides and/or Sézary syndrome. Patients were followed from January 2005 through December 2014. The National Solar Radiation Database was used to ascertain UV exposure in each of the 18 SER registries. The four registries with the highest UV exposure were New Mexico, Los Angeles*, Hawaii, and Utah (high-UV cohort); the four registries with the lowest UV exposure were Seattle, Detroit, Connecticut, and New Jersey (low-UV cohort). Age-adjusted incidence of mycosis fungoides and/or Sézary syndrome were calculated for both the high- and low-UV cohorts. Relative survival at 10 years was also assessed.

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The high- and low-UV cohorts comprised 607 and 991 patients, respectively. The high-UV cohort experienced significantly lower age-adjusted incidence of mycosis fungoides and/or Sézary syndrome compared with the low-UV group (0.542 vs 0.705 per 100,000 persons; [hazard ratio [HR], 1.3; 95% CI, 1.20-1.41; P <.001]). When analyses were stratified by disease stage, between-group differences only remained significant for early-stage disease (0.372 vs 0.439 per 100,000 persons [HR, 1.18; 95% CI, 1.04-1.34; P =.010]). When stratified by race, results were only significant in white patients (0.494 vs 0.657 per 100,000 persons [HR, 1.32; 95% CI, 1.20-1.46; P <.001]). No difference in 10-year survival was observed in either the high- or low-UV cohorts (P =.098). When analyses were stratified by disease stage, however, patients with early-stage disease had greater survival in the high-UV cohort vs the low-UV cohort (P =.007).

These data suggest that environmental UV exposure may influence the development of early-stage mycosis fungoides.

As study limitations, investigators cited the retrospective design, as well as the use of National Solar Radiation Database data as a proxy for sun exposure. “Until more data are available, any potential benefit of seeking active environmental UV exposure needs to be carefully balanced against harm,” the investigators wrote.


DeStefano CB, Desale S, Fernandez SJ, Shenoy AG. The impact of environmental ultraviolet exposure on the clinical course of mycosis fungoides [published online February 11, 2019]. J Am Acad Dermatol. doi:10.1016/j.jaad.2019.02.010