# ZEBRA: pembrolizumab in advanced small bowel adenocarcinoma

Source: https://onco.cc/key-papers/paper-zebra-pembrolizumab-small-bowel-adenocarcinoma-ccr-2021/  
OnCo record `paper-zebra-pembrolizumab-small-bowel-adenocarcinoma-ccr-2021` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Immunotherapy on its own helped only a few patients with advanced small bowel adenocarcinoma, mainly those whose tumours had mismatch repair deficiency, so the drug is reserved for that group.

## Summary

Multicentre single-arm phase 2 study of 40 patients with previously treated advanced small bowel adenocarcinoma given pembrolizumab every three weeks.

The objective response rate was 8 percent and the study did not meet its primary endpoint; responses clustered in patients with mismatch repair deficient or microsatellite instability high tumours, while microsatellite stable disease rarely responded.

## Fields

- Kind: Key paper
- Last checked: 2026-09-18
- Journal: Clinical Cancer Research
- Year: 2021
- DOI: 10.1158/1078-0432.CCR-21-0159
- Authors: Pedersen KS, Foster NR, Overman MJ, et al.
- Findings: Objective response 8 percent overall; the primary endpoint was not met.; Responses were seen in mismatch repair deficient tumours and rarely in microsatellite stable disease.
- What it means: Every small bowel adenocarcinoma should be tested for mismatch repair deficiency, because immunotherapy is worthwhile for those patients and of little use to the rest.
- Caveats: Small single-arm study.; Few dMMR patients were included, so the estimate of benefit in that group is imprecise.

## Sources

- Clin Cancer Res 2021: https://doi.org/10.1158/1078-0432.CCR-21-0159
- PubMed: https://pubmed.ncbi.nlm.nih.gov/33883178/

## Connected records

- cancers: [Advanced and metastatic small bowel adenocarcinoma](https://onco.cc/cancers/advanced-small-bowel-adenocarcinoma/)
- drugs: [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- journals: [Clinical Cancer Research](https://onco.cc/journals/clinical-cancer-research/)

---
JSON: https://onco.cc/api/v1/entities/paper-zebra-pembrolizumab-small-bowel-adenocarcinoma-ccr-2021.json