Effects of Tumor Localization, Age, and Stage on the Outcomes of Gastric and Colorectal Signet Ring Cell Adenocarcinomas

Abstract

Signet ring cell adenocarcinomas (SRCCs) are a rare histological adenocarcinoma subtype, classically thought to have a worse prognosis than conventional adenocarcinomas. The majority of these cancers occur in the stomach, colon, and rectum. Their rarity means that most epidemiological studies into their pathology are often underpowered, and interpretations from these reports are mixed. In this study, we use the Surveillance, Epidemiology, and End Results Program (SEER) database to examine the effects of tumor localization, age, and stage on gastric and colorectal cancer outcomes. For early onset localized and regional gastric cancers, SRCCs have the same overall risk of mortality compared to conventional adenocarcinomas. Over the age of 50 years, SRCCs have worse outcomes across all stages. Gastric SRCCs are 2-3-fold more likely in younger patients, and more heavily favor the distal stomach. Like conventional adenocarcinomas, proximal gastric SRCCs have decreased survival. Across all ages, stages, and locations, colorectal SRCCs have worse outcomes. SRCCs favor the right colon, but outcomes are significantly worse for the left colon and rectal cancers. Relative to adenocarcinomas, colorectal SRCCs have the worst outcomes in younger patients. Overall, these results provide insights into SRCC disease patterns that cannot be surmised outside of population-level data.

Keywords: cancer; chemotherapy; epidemiology; histopathology; radiotherapy; surgery; survival outcomes.

Figure 1

Kaplan-Meier survival curves for gastric cancer. All survivor functions are shown with 95% confidence intervals. (a) All ages, all stages. (b) All ages, local disease. (c) All ages, regional disease. (d) All ages, distant disease. (e) Age < 50, all stages. (f) Age < 50, local disease. (g) Age < 50, regional disease. (h) Age < 50, distant disease. (i) Age ≥ 50, all stages. (j) Age ≥ 50, local disease. (k) Age ≥ 50, regional disease. (l) Age ≥ 50, distant disease. p-values between curves by log-rank test.

Figure 2

Kaplan-Meier survival curves for colorectal cancer. All survivor functions are shown with 95% confidence intervals. (a) All ages, all stages. (b) All ages, local disease. (c) All ages, regional disease. (d) All ages, distant disease. (e) Age < 50, all stages. (f) Age < 50, local disease. (g) Age < 50, regional disease. (h) Age < 50, distant disease. (i) Age ≥ 50, all stages. (j) Age ≥ 50, local disease. (k) Age ≥ 50, regional disease. (l) Age ≥ 50, distant disease. p-values between curves by log-rank test.

Figure 3

Graphical summary of key findings. (A) Percent distribution and hazard ratio comparing adenocarcinomas to signet ring cell adenocarcinomas in the proximal and distal stomach by age. (B) Percent distribution and hazard ratio comparing adenocarcinomas to signet ring cell adenocarcinomas in the right colon, left colon, and rectum by age. Red indicates values for patients < 50 years old, and blue for patients ≥ 50 years old. Hazard ratios display 95% confidence intervals. AdenoCa, adenocarcinoma; SRCC, signet ring cell adenocarcinoma; HR, hazard ratio.