[A Case of Successful Combination of Immune Checkpoint Inhibitors and Radiotherapy for MLH1 Gene-Deficient Colon...

Area of Science:

• Oncology
• Immunotherapy
• Radiation Oncology

Background:

• A 77-year-old female patient presented with advanced transverse colon cancer (Stage IIIc).
• Tumor molecular profiling revealed BRAF mutation, mismatch repair deficiency (dMMR), and microsatellite instability-high (MSI-H) status.
• Initial treatment included extended left hemicolectomy and adjuvant CAPOX chemotherapy.

Purpose of the Study:

• To investigate the efficacy of combining immunotherapy with radiation therapy in a patient with recurrent colon cancer.
• To explore the potential role of the abscopal effect in treatment response.

Main Methods:

• Patient received pembrolizumab for recurrent disease after initial chemotherapy.
• Localized radiation therapy (IMRT) was added to pembrolizumab for a recurrent lesion.
• Treatment response was monitored over time.

Main Results:

• Pembrolizumab monotherapy showed initial limited efficacy with tumor regrowth.
• Combination immuno-radiotherapy resulted in significant tumor shrinkage.
• The patient remained recurrence-free for over two years post-treatment.

Conclusions:

• Combination immunotherapy and radiation therapy can be effective in managing recurrent advanced colon cancer.
• The observed sustained remission suggests a potential abscopal effect mediated by immuno-radiotherapy.
• This case highlights a promising therapeutic strategy for specific molecular subtypes of colon cancer.