Abstract 3421: Epidemiology and survival in patients with extragastric signet ring carcinoma
Authors: Kim Chul , Ulahannan Susanna , Strauss Julius , Del Rivero Jaydira , Duffy Austin , Greten Tim F. , Makarova-Rusher Oxana V. 
Published: July 2016

Background: Signet ring carcinoma (SRC) is a distinct histological phenotype of adenocarcinoma. There are only a few published studies specifying the epidemiology of SRC with extragastric presentation. The purpose of our study was to define the most common primary sites of extragastric SRC, determine the incidence, and to compare survival by primary site and disease stage.

Methods: The Surveillance Epidemiology and End Result (SEER) database was examined from 2000 to 2012 in order to identify SRC histology (8490) and determine its most common primary sites, incidence, and survival by site and stage. The five most common primary extragastric sites were identified by utilizing ICD-0-3/WHO 2008 classification. Age-adjusted incidence rates for extragastric SRC were calculated and compared to gastric SRC. Relative survival (RS) and overall survival (OS) at 1 and 3 years were analyzed by primary site and stage using Kaplan-Meier method. Chi-square test was used for categorical variables.

Results: A total of 24,522 histologically confirmed cases of SRC were identified, and SRC comprised 0.5% of all malignant neoplasms. Among cases with known histological grade, 89.7% had poorly differentiated tumors. Overall, digestive system origin was recorded for 90% of SRC cases. Approximately half (44.2%) of primary SRC tumors were detected outside of the stomach. The most common primary sites for extragastric SRC were colon (40.5%), esophagus (11.9%), rectum (9.8%), lung/bronchus (7.3%), and pancreas (4.7%). The incidence rates for common extragastric SRC were much lower than for gastric SRC, and were higher for males than females (p&lt;0.001). Incidence profile differed by gender as breast was among top five SRC anatomical sites for females. Clinically, distant metastatic disease was more often diagnosed in patients with pancreatic (66.3%) and lung/bronchus (73.8%) SRC than SRC of the stomach (43.5%) (p&lt;0.01). Survival varied substantially by primary site. Pancreatic SRC had the worst survival and colorectal the most favorable. For example, among patients with stage IV disease, 1-year RS was 43.9% (95% CI = 41.1-46.6) for colorectal, 25.5% (95% CI = 20.6-30.6) for lung/bronchus, 20.9% (95% CI = 16.2-26.1) for esophageal, and only 10.7% (95% CI = 6.5-15.9) for pancreatic primary SRC. In concordance with 1-year RS, 3-year RS was 9.9% (95% CI = 8.2-11.9) for colorectal vs. 0.0% for pancreatic SRC.

Conclusion: Our study indicated that extragastric SRC most commonly occurs in the colorectum, esophagus and lung/bronchus. We confirmed that the primary site substantially impacts survival. Thus, development of unique molecular or histologic markers may help to identify the organ of origin and thereby determine prognosis in these phenotypically similar neoplasms.

Citation Format: Chul Kim, Susanna Ulahannan, Julius Strauss, Jaydira Del Rivero, Austin Duffy, Tim F. Greten, Oxana V. Makarova-Rusher. Epidemiology and survival in patients with extragastric signet ring carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3421.