# Tumor–stroma ratio in colitis-associated colorectal cancer

## TL;DR

High stroma content in colitis-associated colorectal cancer is linked to worse survival and is more common in younger patients.

## Contribution

This study is the first to show that tumor-stroma ratio correlates with survival in colitis-associated colorectal cancer.

## Key findings

- High stroma content (TSR > 50%) was associated with lower 5-year survival (32% vs. 71%).
- High stroma tumors were more common in patients diagnosed before age 60.
- TSR is a prognostic marker in colitis-associated colorectal cancer, similar to sporadic CRC.

## Abstract

High stroma content, as measured by tumor-stroma ratio (TSR), is generally a negative prognostic parameter for epithelial cancers, including sporadic colorectal cancer (sCRC). Inflammatory bowel disease patients have higher risk for colorectal cancer than the background population. Evidence suggests that this colitis-associated colorectal cancer (CAC) is more aggressive and occurs at younger age than sCRC. CAC also differs from sCRC in oncogenesis and prognosis. This study tests the hypothesis that TSR in CAC tumors correlates with survival. Age at CAC diagnosis relative to TSR was also explored. TSR was quantified in 36 CAC cases. In routine hematoxylin–eosin staining, the amount of stroma was estimated in categorical steps of 10% increments per image field. The area with highest amount of stroma and tumor tissue at all quadrants of the visual field boundary was scored for TSR. For statistical analysis, tumors were divided into stroma-high (> 50%) or stroma-low (≤ 50%). Of all cases, 22 were stroma-high and 14 were stroma-low. Five-year survival in the stroma-high group was 32% (n = 22), compared to 71% (n = 14) in the stroma-low group (p = 0.049). High stroma content was more frequent if cancer diagnosis was before 60 years of age (17/23) compared to after 60 years of age (5/13). Despite differences in oncogenesis and tumor biology in CAC compared to sCRC, high stroma content also predicts worse outcome in CAC and is particularly common in younger patients.