This retrospective cohort study evaluated clinicopathologic and genomic factors associated with relapse, and the efficacy of adjuvant chemotherapy, in 439 patients with localized (stage I–III) appendiceal adenocarcinoma (AA) treated at MD Anderson (Jan 2000–Feb 2024; median follow-up 62.6 months), with validation of stage II patients from Memorial Sloan Kettering (n=128).
Relapse was uncommon: only 9.4% (19/202) of surgical patients relapsed, with 5-year OS of 95.7% (no relapse) vs 77.2% (relapse; HR 5.50). Mucinous (HR 5.60) and enteric-type (HR 6.60) histologies and T4 disease (HR 3.30) were independently associated with relapse, but adjuvant chemotherapy showed no benefit on RFS (multivariable HR 0.98, P=.90) or OS (multivariable HR 0.71, P=.53). TP53 mutation in goblet cell tumors (HR 6.93) and GNAS mutation in non-goblet tumors (HR 17.0) flagged higher relapse risk.
Retrospective design with inherent selection bias; adjuvant chemotherapy was likely preferentially given to higher-risk patients, limiting causal interpretation despite multivariable adjustment. Overall relapse rates are low, limiting statistical power for subgroup analyses.
Routine adjuvant chemotherapy after resection of localized appendiceal adenocarcinoma does not appear to improve survival and should not be standard practice. Risk stratification using histologic subtype (mucinous or enteric-type over goblet cell) and molecular profiling (TP53 in goblet cell, GNAS in non-goblet) can help identify the minority of patients at meaningful relapse risk.
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