Intro: Mycosis Fungoides (MF) is the most common cutaneous T cell lymphoma and is over-represented by black men. Those presenting with early stage disease are more likely to become long term survivors than those presenting with advanced stage disease (≥ IIB) (Agar NS et al, JCO, 2010). The cornerstone of treatment for early stage disease is skin directed therapy which includes topical modalities and ultraviolet (UV) light treatment (psoralen UVA or narrow-band UVB). In its early stages, MF can clinically and histologically mimic benign skin conditions, not uncommonly resulting in a diagnostic delay. It is possible that environmental UV exposure may provide disease control during its early stages and consequently result in a decreased reported incidence. Based on our anecdotal experience treating patients with MF at an urban hospital in Washington D.C., we hypothesized that blacks have a more aggressive disease biology than whites, and that patients with high environmental UV exposures have better disease control than those with low UV exposures. We accessed the Surveillance, Epidemiology, and End Results (SEER) 18 database, which encompasses 27.8% of the U.S. population, to test these hypotheses.
Methods: Adults aged 20-85+ with MF +/- Sezary Syndrome (ICD-O codes 9700/3 & 9701/3) were analyzed from the SEER-18 database over a ten-year span (January 2005 to December 2014). Patients with advanced stage (≥ IIB per 2004 AJCC TNM staging) were included for racial assessments, whereas patients with all stages were included for UV exposure assessments. To assess the impacts of access to care on reported incidence and survival, a separate analysis was performed exclusively on patients with insurance and who received chemotherapy (surrogates for access to healthcare). Since insurance recoding began in 2007, the years 2007-2014 were selected for these assessments. Geographic areas were selected based on the National Cancer Institute's Geographic Information Systems map on annual cumulative county level UV exposure (measured in Wh/m2) as well as the National Solar Radiation Database. The SEER registries in the top and bottom quartiles for cumulative UV exposure were identified as New Mexico, Los Angeles, Hawaii, and Utah (High UV cohort) and Seattle, Detroit, Connecticut and New Jersey (Low UV cohort). Age-adjusted incidence and 5-year relative survival were determined. The chi-square test was used to assess for associations based on race and UV exposure.
Results: Graphics on incidence and survival are demonstrated in Figures 1 & 2. Blacks were more likely to present with advanced stage disease than whites, even among those with health insurance (p<0.001). Blacks had a lower chance of achieving long-term survival than whites (p=0.015), which is likely attributable to differences in access to healthcare as this association was no longer appreciated when the analysis was performed on patients with health insurance and who received chemotherapy (p=0.281). The high UV exposure cohort had a lower incidence of MF/SS than the low UV exposure cohort (p<0.001). When stratified by race, this association was only appreciated in whites and not blacks (p<0.001 & p=0.639, respectively). There was no difference in long term survival between the high and low UV cohorts, irrespective of race (p=0.128).
Conclusions: Blacks were more likely to present with advanced stage disease than whites. Racial differences in survival may have to do more with sociodemographic factors affecting access to healthcare than differences in disease biology. High UV exposure, a critical component of the armamentarium for early stage disease, was associated with a lower incidence of MF/SS, suggesting that environmental UV exposure may play a role in disease control.
No relevant conflicts of interest to declare.
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