There is an increased incidence of locally staged Merkel cell carcinoma (MCC) among patients who live in rural areas of the United States, compared with those in urban and metropolitan areas, yet overall survival is worse in rural areas.
This paradox was discovered in an analysis of data from the Surveillance, Epidemiology, and End Results (SEER) Program that primary author Bryan T. Carroll, MD, PhD, and colleagues presented during a virtual abstract session at the annual meeting of the American Society for Dermatologic Surgery.
“MCC is a rare and aggressive neoplasm of the skin with high mortality,” said coauthor Emma Larson, MD, a dermatology clinical research fellow at University Hospitals of Cleveland. “Previous studies have demonstrated that MCC survival is lower in low–dermatologist density areas. Associations are difficult to characterize without historical staging data aggregated from large registries. We hypothesized that decreased MCC survival is associated with rural counties.”
The researchers used 18 registries from the November 2019 SEER database to retrospectively evaluate adults who were diagnosed with MCC between 2004 and 2015 as confirmed by positive histology. Study endpoints were SEER historic stage at diagnosis and 5-year survival. MCC cases were stratified by 2013 USDA urban-rural continuum codes, which defines metropolitan counties as those with a population of 1 million or more, urban counties as those with a population of less than 1 million, and rural counties as nonmetropolitan counties not adjacent to a metropolitan area.
A total of 6,291 cases with a mean age of 75 years were included in the final analysis: 3,750 from metro areas, 2,235 from urban areas, and 306 from rural areas. A higher proportion of MCC patients from rural areas were male (69% vs. 62% from metro areas and 64% from urban areas) and white (97% vs. 95% and 96%, respectively). “This may contribute to differences in MCC care,” Larson said. “However, we also found that there is an increased incidence of locally staged disease in rural areas (51%) than in metro (44%) or urban (45%) areas (P = .02). In addition, fewer lymph node surgeries were performed in rural (50%) and urban (51%) areas than in metro areas (45%; P = .01).”
Overall survival was worse among patients in rural areas (a mean of 34 months), compared with those in urban (a mean of 41 months) and metro areas (a mean of 47 months; P = .02). “This may be due to the fact that rural counties have the higher risk factors for MCC incidence and death, but when we account for the confounders, including sex, age, race, and MCC stage, we still found a difference in overall survival in rural counties, compared to metro and urban counties,” Larson said.
Carroll, an associate professor of dermatology at University Hospitals of Cleveland, characterized the finding as “not what you’d expect with a higher incidence of local disease. Therefore, there is the potential for mis-staging in rural counties, where we did see that the interrogation of lymph nodes was done less frequently than in urban centers, which were more aligned with National Comprehensive Cancer Network guidelines during this time period. Still, after correction, rural location is still associated with a higher MCC mortality. There is a need for us to further interrogate what the causes are for this disparity in care between rural and urban centers.”
The other study authors were Dustin DeMeo and Christian Scheufele, MD. The researchers reported having no relevant financial disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.