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A CASE REPORT OF AN 11-YEAR-OLD MALE WITH METASTATIC COLON CANCER
Farhan Azad
*1, Clive J. Miranda
21Inova Fairfax Hospital, Falls Church, VA; 2Creighton University, Omaha, NE
An 11-year-old male initially presented with a headache and was found to have a left temporal mass suspicious of a glioma, which was resected, followed by adjuvant proton therapy. The biopsy revealed left frontal high-grade glioma, hypermutant, with mutations in PMS2, MLH1, SETD2, PI3KA, PDGFRA, EZH2, PTEN, ATM, BRCA2, TP53, NF1, POLD1 in genetic testing. It was thought that the glioma may have developed in the setting of being mismatch repair deficient (MMRD). 4 weeks later, the patient was readmitted with blood in his stool. CT abdomen showed numerous liver lesions suspicious of metastasis. A colonoscopy revealed a malignant tumor in the rectum and the cecum, the biopsy was positive for adenocarcinoma. The patient was given pembrolizumab inpatient, based on the Keynote 177 trial data that showed a high response rate with the use of pembrolizumab monotherapy compared to first-line chemotherapy in MMRD patients 18 years of age or older. Unfortunately, the patient had progression of disease in the liver after 2 cycles. He was discharged with plans for a change of therapy to a combination of ipilimumab and nivolumab. The decision was made based on the Checkmate 8HW study published in 2024, which also included MMRD patients 18 years of age or older and showed survival benefits with combination immunotherapy over chemotherapy. Our patient had a PMS2 biallelic germline inactivation and a hypermutant high-grade glioma with synchronous multifocal metastatic colon cancer. His high-grade glioma had a POLD1 mutation, which has been shown to predict a great response to immunotherapy in literature. The case represents a rare instance of a common malignancy seen in adults, colorectal adenocarcinoma. A paucity of data exists for this entity in younger patients. The correct management will often need collaboration from both pediatric and adult oncologists, and the extrapolation of information from clinical trials that includes adult participants only.
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