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Colorectal

E105: Location has Prognostic Impact on the Outcomes of Colorectal Mucinous Adenocarcinomas

Introduction: Mucinous (colloid) adenocarcinomas (MAs) are a rare histological subtype defined by extracellular mucin comprising more than 50% of the tumor. These tumors are on a continuum of mucin-producing malignancies with signet ring cell adenocarcinomas (SRCCs), which instead produce intracellular mucin. Mucin-containing cancers occur primarily in the stomach and colon, where for SRCCs, outcomes are significantly worse in the proximal stomach and the rectum. It is not known if MAs have location associated outcomes.

Methods: In this study, we use the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program (SEER) database to examine the clinical and demographic effects of tumor localization, age, sex, and stage on colorectal and gastric cancer outcomes for MAs. Hazard ratios (HR) for mortality are corrected for age, sex, race, detection stage, grade differentiation, surgery, radiotherapy, and chemotherapy.

Results: MAs were more common in the right colon compared to conventional adenocarcinomas (54.0% vs. 33.4%), particularly in females (58.6% vs. 37.9%). In early onset cancer (< 50 years of age), right colon MAs occurred 47.2% of the time in females (vs. 46.2% for males), and in the ≥50-year-old group, this increased to 59.9% in females (vs. 47.2% for males). Conventional adenocarcinomas showed no age bias in males, having composed about 21% of all cancers in both age groups, with an increase to 39.8% from 30.1% between older and younger females, respectively. Regarding disease state at presentation, females under 50 years old present with distant disease in the right colon 40.9% of the time, as opposed to 31.4% with adenocarcinomas. Despite this, right colon MAs had slightly better or equivalent outcomes across all stages and ages compared to conventional adenocarcinomas (HR mortality with 95% confidence interval (CI) 0.89 (0.87-0.91)). Outcomes were progressively worse compared to conventional adenocarcinomas for left colon (HR 1.16 (1.12-1.20)) and rectal cancers (HR 1.28 (1.24-1.32)). This trend was identical for both early onset disease (< 50 years old), and late onset disease (≥50 years old). Unlike SRCCs, MAs had similar outcomes to conventional adenocarcinomas in all stomach locations, with proximal stomach HR of 1.17 (1.08-1.26), and distal stomach HR of 1.07 (0.96-1.19).

Conclusions: Overall, these results suggest that MAs have different tumor biology in the left colon and rectum compared to the right colon that promote pathogenesis. Decoding this phenomenon could lead to more effectively tailored patient treatment regimens.

Learning Objectives:

  • Describe the distribution of mucinous adenocarcinomas in the colon (and stomach), and compare them to conventional adenocarcinomas and signet ring cell carcinomas.
  • Describe the effects of colorectal location on overall patient survival in patients with mucinous adenocarcinomas.
  • Describe both similarities and differences between mucinous adenocarcinomas and signet ring cell adenocarcinomas with respect to colorectal (and stomach) location for different age, sex, and stage groups.