# Unveiling ctDNA Response: Immune Checkpoint Blockade Therapy in a Patient with POLE Mutation-Associated Early-Onset Colon Cancer

## TL;DR

A young man with a rare genetic mutation in his colorectal cancer responded well to immunotherapy, showing promise for personalized cancer treatments.

## Contribution

This case highlights the potential of immunotherapy for POLE-mutated early-onset colorectal cancer.

## Key findings

- A patient with POLE-mutated colorectal cancer showed dramatic tumor shrinkage after immunotherapy.
- Blood tests revealed a near disappearance of cancer-related DNA following treatment.
- The patient remained cancer-free two years after starting immunotherapy.

## Abstract

Colorectal cancer is one of the most common cancers, and alarmingly, an increasing number young people under 50 are being diagnosed with it. The reasons for this are not fully understood, but certain genetic changes may play a part. One of these involves a gene called POLE, which normally helps to repair DNA mistakes. When POLE is mutated, cells collect too many errors, but this also makes the cancer more visible to the body’s immune system. This report details a case of a young man with advanced colorectal cancer carrying the POLE mutation who did not respond to regular chemotherapy. However, once he started immunotherapy, a treatment that helps the immune system to fight cancer, his tumors shrank dramatically. Blood tests showed that his cancer-related DNA nearly vanished, and two years later, he remains cancer-free. This story shows how understanding a tumor’s unique genetics can lead to better, more personalized treatments, and offers hope for patients facing similar situations in the future.

Colorectal cancer (CRC) is the third most common malignancy worldwide and the second leading cause of cancer-related mortality in the United States. The incidence of early-onset colorectal cancer (EOCRC) has been increasing over the past several decades. While the etiologies for this rising incidence remain unclear, genetic factors likely play an important role. DNA polymerase epsilon (POLE) mutations occur at a higher rate than average-onset colorectal cancer (AOCRC). DNA polymerase epsilon (Pol ε) is a high-fidelity, processive polymerase that is a promising target for immune checkpoint inhibitors due to its association with various human malignancies, including colorectal cancer. EOCRC remains a major area of focus, and POLE mutations leading to the high-TMB subtype constitute a potential therapeutic target.