The clinical landscape of POLE-mutant colorectal cancer: a retrospective analysis of real-world outcome

BACKGROUND: Pathogenic mutations in the POLE gene disrupt its proofreading function during DNA replication, causing an accumulation of erroneous nucleotide incorporations. This defect leads to a significantly elevated tumor mutation burden (TMB) and increased generation of tumor neoantigens. These molecular characteristics suggest a potential association between POLE-mutant tumors and distinct prognostic outcomes in colorectal cancer (CRC); however, clinical evidence supporting this correlation remains limited. METHODS: We retrospectively collected a cohort of CRC patients harboring pathogenic POLE mutations. Comparative analyses were performed between POLE-mutant and POLE wild-type CRCs regarding their clinical characteristics, prognostic outcomes, and genomic profiles. Additionally, we evaluated the response to immunotherapy in metastatic POLE-mutant CRC cases. RESULTS: Among 35,108 CRC patients, pathogenic POLE mutations were identified in 261 individuals, accounting for 0.74% of the cohort. The median age at diagnosis for POLE-mutant patients was 48 years, with a male predominance (74.4%) and a substantial proportion (50.4%) of tumors localized in the right-sided colon. All patients with pathogenic POLE mutations exhibited hypermutated phenotypes, characterized by a median TMB of 235.26 mutations per megabase (range: 71.20-719.00 mutations/Mb). In stage II CRC, POLE mutations were significantly associated with a reduced risk of recurrence (hazard ratio [HR] 0.344, 95% confidence interval [CI] 0.157-0.754, p = 0.008) when compared to POLE wild-type, microsatellite stable CRC patients. However, this association was not evident in stage III patients (HR 1.004, 95% CI 0.490-2.057, p = 0.992). Importantly, the incorporation of immune checkpoint inhibitors in first-line treatment regimens significantly improved progression-free survival (HR = 0.247, 95% CI 0.117-0.552, p = 0.0002) and overall survival (HR = 0.317, 95% CI 0.103-1.143, p = 0.0832) in metastatic CRC patients with pathogenic POLE mutations. CONCLUSIONS: Pathogenic POLE-mutant CRC constitutes a relatively rare, yet clinically important, subtype. These cancers exhibit distinct clinicopathological and genomic features. Our results indicate that mutations in the POLE gene may serve as a valuable prognostic marker and a potential indicator of benefit to immunotherapy in CRC, offering promising avenues for personalized treatment strategies.