Uncovering molecular pathways in appendiceal cancer: A comprehensive characterization for precision oncology

Appendiceal cancer (AC) is a rare and understudied gastrointestinal malignancy with a rising incidence. Molecular characterization of this disease is limited. In this work, we analyzed molecular alterations of appendiceal cancer across seven key oncogenic pathways- RTK/RAS, TP53, MAPK, PI3K, TGF-β, WNT and JAK/STAT-stratified by tumor subtype and stage, to identify clinically relevant molecular signatures that could inform precision oncology strategies.

A cohort of 861 AC cases (402 primary and 459 metastatic) were analyzed from publicly available genomic datasets. Samples were stratified by tumor stage, histology (Group 1-LAMN/Low-Grade Adenocarcinoma; Group 2-Moderate-to High-Grade Adenocarcinoma; Group 3-Goblet Cell Adenocarcinoma; Group 4-Signet Ring Cell Adenocarcinoma), and sex. Mutation frequencies and tumor mutational burden (TMB) were evaluated across the seven pathways. Statistical comparisons were performed using chi-squared tests, and overall survival (OS) was assessed using Kaplan-Meier analysis.

In primary AC, alterations in the RTK/RAS pathway (p = 0.006) and MAPK pathway (p = 0.019) were significantly associated with improved overall survival (OS). In metastatic AC, TP53 pathway alterations correlated with poorer OS (p = 0.012). Comparative analyses revealed distinct molecular differences between primary and metastatic tumors: PI3K pathway alterations were more frequent in primary AC than in metastatic cases (18.2% vs. 12.9%, p = 0.03). Similarly, within the TGF-β pathway, SMAD4 mutations were enriched in primary compared to metastatic tumors (6.7% vs. 2.8%, p = 0.01). Histology-based stratification confirmed differential pathway enrichment: PI3K alterations were higher in primary vs. metastatic tumors in Group 2 (22.1% vs. 11.0%, p = 0.008), and TP53 alterations were less frequent in primary vs. metastatic Group 3 cases (15.7% vs. 30.0%, p = 0.037). Genes in the RTK/RAS pathway-including SOS1 (p = 0.04), KIT (p = 0.001), and RAF1 (p = 0.04)-were more commonly mutated in primary tumors. Likewise, the TP53 pathway gene CDKN2A was more frequently altered in primary than in metastatic samples (p = 0.02). Missense mutations were the predominant alteration type across all cohorts. Distinct oncogenic pathway remodeling characterizes appendiceal cancer progression, with primary tumors enriched for PI3K and SMAD4 alterations and metastatic Goblet Cell Adenocarcinoma demonstrating increased TP53 pathway disruption.

This study offers a comprehensive molecular characterization of AC, comparing distinct oncogenic pathway signatures between primary and metastatic disease. The identification of pathway-specific alterations offers valuable insights into the molecular heterogeneity of AC and highlights opportunities for pathway-targeted therapies. These findings emphasize the importance of integrative molecular profiling to advance precision oncology and improve outcomes for patients with this rare malignancy.