Survival Outcomes and Prognostic Factors in Metastatic Unresectable Appendiceal Adenocarcinoma Treated with...

Appendiceal adenocarcinoma is a rare malignancy, and data guiding its systemic treatment in metastatic settings are limited. This study aimed to determine the clinical outcomes, treatment efficacy, biomarkers, and prognostic factors in patients with metastatic or unresectable appendiceal adenocarcinoma receiving palliative chemotherapy.

We retrospectively reviewed patients with metastatic appendiceal adenocarcinoma who received first-line palliative systemic chemotherapy at the Peter MacCallum Cancer Centre between January 2015 and December 2024.

Of the 40 patients included, fluoropyrimidine-based doublet regimens were most commonly used (82.5%) in first-line setting, achieving an objective response rate of 39.4%. Median overall survival (OS) was 21.6 months, and median first-line progression-free survival (PFS) was 8.9 months. 22 patients (55.0%) received second-line treatment. Median OS and PFS were 21.6 and 8.9 months, respectively, among patients treated with oxaliplatin-based doublet regimens, and 66.4 and 10.8 months, respectively, among those treated with irinotecan-based doublet regimens. Molecular biomarker testing was performed in 35 patients (87.5%). KRAS and NRAS mutations were identified in 68.6% and 2.9% of tested patients, respectively. Factors associated with poorer OS included male sex, elevated carcinoembryonic antigen levels, and overweight status. Bevacizumab use was not clearly associated with survival.

Palliative systemic chemotherapy, particularly fluoropyrimidine-based doublet regimens, appears to be a reasonable and effective treatment option for patients with advanced appendiceal adenocarcinoma. Although this study was underpowered for formal comparison, the numerically longer OS and PFS of irinotecan-based regimens are hypothesis-generating and support further prospective evaluation. Molecular profiling emphasizes the need for personalized targeted therapeutic strategies. The identified prognostic factors may help guide risk stratification and patient counseling for treatment planning.