# Treatment and survival of non-metastatic rectal cancer in patients with inflammatory bowel disease: nationwide cohort study

## TL;DR

This study found that patients with rectal cancer and inflammatory bowel disease had similar long-term survival rates as those without the disease, despite a higher risk of recurrence in the first year after surgery.

## Contribution

The study provides new insights into recurrence-free survival in rectal cancer patients with inflammatory bowel disease using a nationwide cohort.

## Key findings

- Patients with inflammatory bowel disease had lower recurrence-free survival during the first year after surgery.
- Long-term recurrence-free survival was similar between patients with and without inflammatory bowel disease.
- Neoadjuvant radiotherapy/chemoradiotherapy was used similarly in both groups.

## Abstract

Patients with inflammatory bowel disease have an increased risk of colorectal cancer. There is a scarcity of large studies with a focus on rectal cancer in patients with inflammatory bowel disease. This study aimed to compare survival in resected patients with rectal cancer with and without inflammatory bowel disease.

This national population-based study used the Colorectal Cancer Data Base. All Swedish patients ≥18 years of age with a diagnosis of stage I–III rectal cancer between 1997 and 2021, surgically treated with curative intent, were included and followed up until 2022. The outcome of interest was recurrence-free survival. Flexible parametric survival models adjusted for time since surgery, year of diagnosis, sex, age at diagnosis, and Charlson Co-morbidity Index were used to estimate proportional and time-dependent hazard ratios of recurrence-free survival with 95% confidence intervals.

Overall, 22 082 patients with rectal cancer were included, among whom 323 (1.5%) had inflammatory bowel disease. Neoadjuvant radiotherapy/chemoradiotherapy was given to 55% and 63% of patients with and without inflammatory bowel disease respectively. The median follow-up time was 5.2 years (interquartile range (i.q.r.) 2.3–10) in patients with inflammatory bowel disease and 5.9 years (i.q.r. 2.9–10) in patients without inflammatory bowel disease. Based on the adjusted proportional hazards model, no overall difference in recurrence-free survival was found (HR 1.05, 95% c.i. 0.87 to 1.26). In the time-dependent adjusted model, patients with rectal cancer with inflammatory bowel disease experienced a lower recurrence-free survival during the first year after surgery (1 year HR 1.36, 95% c.i. 1.06 to 1.73), after which there was no difference in comparison with patients without inflammatory bowel disease (5 years HR 0.77, 95% c.i. 0.56 to 1.06).

Despite lower recurrence-free survival during the first year among those with inflammatory bowel disease, there were no long-term differences between patients with or without inflammatory bowel disease.

In this national cohort study of patients with rectal cancer and inflammatory bowel disease, the recurrence-free survival was time dependent. Despite lower recurrence-free survival during the first year among those with inflammatory bowel disease there were no long-term differences between patients with or without inflammatory bowel disease. Neoadjuvant radiotherapy/chemoradiotherapy was used to the same extent in both groups.