Onkologie. 2026:20(1):40-42 | DOI: 10.36290/xon.2026.006

Complete remission of locoregionally advanced MSI-H rectal cancer treated with immunotherapy

Marián Liberko^{1, 2}, Renata Soumarová^{1, 2}

¹ Onkologická klinika, 3. LF UK a FNKV, Praha

² 3. lékařská fakulta Univerzity Karlovy, Praha

The presence of dMMR status or MSI-H phenotype is the strongest predictor of immunotherapy efficacy across a range of malignancies. We present the case of a young patient with MSI-H locoregionally advanced rectal cancer who was treated with 6 months of nivolumab monotherapy. A complete clinical response (cCR) was achieved, allowing for a non-surgical approach and organ preservation. This case highlights a fundamental change in treatment strategy for selected colorectal cancers in the era of immunotherapy and emphasizes the critical importance of routine MSI status testing in all newly diagnosed patients with rectal cancer. Early identification of MSI-H can significantly influence therapeutic decisions and potentially spare patients the morbidity associated with radical surgery.

Keywords: rectal cancer, MSI-H, immunotherapy, clinical complete response.

Accepted: March 2, 2026; Published: March 16, 2026  Show citation