Demographics, Characteristics, and Incidence Trends of Rectal Neuroendocrine Tumors in the US: A Nationwide Analysis Using the SEER and USCS Databases

Introduction: Previous data showed increasing incidence of rectal neuroendocrine (RNET) in the US. However, there are limited data on recent RENT characteristics and trends in age-specific populations. Therefore, the aim of this study was to investigate demographics, characteristics, and trends of RNET in nationwide databases, the Surveillance Epidemiology and End Results (SEER) database, and the United States Cancer Statistics Database (USCS). Methods: Demographic and characteristics data between 2000-2019 were obtained from the SEER 22 database, covering 47.9% of US population, while incidence data were obtained from the USCS database, covering 98% of US population, using SEER*Stat software. RNET were identified using ICD-O-3 codes. The population was categorized into older adults, aged≥55 years, and younger adults, aged< 55 years. Data was presented as absolute numbers with percentages. Chi square test was utilized to compare categorical variables between age groups, P-value cutoff at 0.05. Time-trends were estimated as average annual percentage change (AAPC) using Joinpoint regression and Monte Carlo permutation analysis. Results: There were 31,251 patients diagnosed with RNET reported in the SEER database between 2000-2019. In younger adults, most patients were women (25.3%), while in older adults, most were men (26.1%), both displaying significant difference (P < 0.0001) (Table 1). Stratifying by race, most were Non-Hispanic White and for each race there was a significant difference in number of patients between the 2 age groups (P < 0.0001). Most patients were married and were diagnosed at an early stage of disease (in situ and localized) in both age groups compared to late stage (regional and distant). Incidence rates of RNET were increasing in early and late-stage tumors (AAPC = 2.84, P < 0.001; 1.98, P = 0.001). In older adults, the rates were stable in early and late-stage tumors (AAPC = 0.46, P = 0.18; AAPC = 1.00, P = 0.07). However, in younger adults, the rates were increasing in early stage and late-stage tumors (AAPC = 4.58, P < 0.001; 3.69, P < 0.001) (Figure 1). Conclusion: Our study evaluating RNET in the US using 2 nationwide databases, SEER and USCS, covering nearly all of US population, show significant differences in RENT characteristics and patients’ demographics between younger and older adults. We also show that early and late-stage RENT incidence has been increasing in the US, and this trend was driven by younger adults. Future studies are warranted to assess mortality and outcomes of RNET. Table 1. - Demographics and Characteristics of Rectal Neuroendocrine Tumors in the US Categorized by Age Group Variable Younger Adults (< 55 years) Older Adults (≥55 years) P-Value Number of Patients 15,366 15,915 Sex Men 7,423 (23.7%) 8,176 (26.1%) < 0.0001 Women 7,943 (25.3%) 7,739 (24.7%) Race Non-Hispanic White 6,440 (43.9%) 7,140 (46.3%) < 0.0001 Non-Hispanic Black 3,597 (24.5%) 3,915 (25.4%) Hispanic 2,742 (18.7%) 2,444 (15.8%) Non-Hispanic American Indian/Alaska Native 107 (0.73%) 84 (0.54%) Non-Hispanic Asian or Pacific Islander 1,788 (12.2%) 1,848 (12.0%) Marital Status Single (never married) 2,557 (26.2%) 1,712 (16.9%) < 0.0001 Married (including common law) 6,256 (64.1%) 6,329 (62.4%) Separated 137 (1.4%) 147 (1.5%) Divorced 675 (6.9%) 948 (9.4%) Widowed 133 (1.4%) 999 (9.9%) County Metropolitan 14,103 (92.1%) 14,362 (90.4%) < 0.0001 Non-Metropolitan 1,218 (7.95%) 1,526 (9.60%) Stage at Diagnosis Early (In Situ and Localized) 10,617 (95.0%) 10,434 (90.9%) < 0.0001 Late (Regional and Distant) 554 (4.96%) 1,045 (9.10%) Figure 1.: Time-trends of rectal neuroendocrine tumors incidence rates in the US categorized by stage at diagnosis in different age group.