May 22, 2019
2 min read

Thyroid cancer survival higher for US city residents

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More cases of thyroid cancer are found among those living in urban areas in the U.S., but this population also has a higher rate of survival compared with those in rural areas, according to findings published in The Journal of Rural Health.

Sabha Ganai

“Incidence of thyroid cancer is increasing in the U.S. and many other countries, theoretically due to overdiagnosis from increased use of imaging technologies like ultrasound,” Sabha Ganai, MD, PhD, MPH, FACS, an assistant professor in the department of surgery and the director of gastrointestinal oncology for the Simmons Cancer Institute at Southern Illinois University School of Medicine, told Endocrine Today. “Because there are differences in access to care for patients in rural settings, we hypothesized that incidence would be different from urban populations.”

Ganai and colleagues identified 119,797 cases of thyroid cancer in 18 regions in the United States from the Surveillance, Epidemiology and End Results cancer registry. Each case was categorized as a patient from an urban, adjacent to urban or rural county based on U.S. Department of Agriculture Rural-Urban Continuum Codes.

Urban areas contained the largest number of thyroid cancer cases (n = 108,821). The incidence rate was higher for those in such areas (11.2 per 100,000) compared with those in rural (10.1 per 100,00) and adjacent areas (9.8 per 100,000; P < .05 for all), with the researchers noting that this held for all races and ethnicities. Those in urban areas also experienced a larger increase in incidence during the study period (6.65 annual percentage change) compared with those in adjacent (5.82 annual percentage change) and rural areas (5.77 annual percentage change; P < .05 for all).

“Although this study is not able to determine causality, the higher incidence seen in urban counties, regardless of race/ethnicity, suggests that patients in urban counties may be undergoing a higher frequency of diagnostic ultrasounds or fine-needle aspirations, may incur higher levels of unrecognized carcinogens, or simply have greater access to care,” the researchers wrote.

According to the researchers, survival rates for those from urban areas who had thyroid cancer were higher at 1 year (98.2% vs. 97.1%), 5 years (97.7% vs. 96%) and 10 years (95.9% vs. 93.2%) compared with those from rural areas (P < .05 for all). When compared with those from adjacent areas, those from urban areas had a significantly higher survival rate only at 5 years (97.7% vs. 96.2%).

“Survival was worse between populations who lived in rural counties that were not adjacent to an urban county, in comparison to rural counties that were next to urban centers, suggesting that an access issue may have survival implications,” Ganai said. “The data may suggest that observational intensity may need to be adjusted appropriately to prevent overdiagnosis of subclinical cancers but ensure appropriate management of more aggressive cancers.” – by Phil Neuffer

Disclosures: The authors report no relevant financial disclosures.