Abstract 226P
Background
Appendiceal adenocarcinoma (AA) encompasses a heterogenous mix of histologic subtypes and most commonly presents with peritoneal metastases. Data regarding risk of relapse and benefit of adjuvant chemotherapy (AC) in patients with stages I–III AA is limited.
Methods
The Foundry software platform was used to query the MD Anderson Cancer Center (MDA) internal database to extract clinical, demographic, and molecular data from patients with AA diagnosed between 2000 and 2024.
Results
Out of 464 patients diagnosed with localized AA, 210 underwent surgery at MDA. The relapse rate for MDA surgical cohort was 9.5% (20 of 210), with a median time to relapse of 23 months (range 0.2–95). Evaluating all 464 localized AA patients, histologic subtype was significantly associated with risk of relapse, with signet ring cell (SRC, 47%, 7 of 15) tumors having greatest risk followed by mucinous (36%, 64 of 180), colonic-type (23%, 21 of 92) and goblet cell (GCA, 7.3%, 13 of 177) tumors having lowest risk (chi square overall p=6.4e-10). The clinical features associated with relapse were different among four histologic subtypes. For example, grade was associated with relapse in GCA (0% G1 & G2, 11% G3, p = 0.02) and colonic-type (0% G1, 16% G2, 37% G3) but, interestingly, grade was not associated with relapse in mucinous tumors (29%, 33%, 35% for G1, G2, G3, respectively, p=0.66). Importantly features like perineural invasion (OR 0.62 trending toward less relapse, p =0.065) and lympho-vascular invasion (OR 1.0, p =0.97) were not associated with relapse in AA. Outcomes were favorable for entire cohort with a 5-year OS rate of 96%, this was 78% for the 105 patients who relapsed, of whom 63 (60%) underwent cytoreductive surgery after relapse. There was a trend towards greater relapse among patients who received AC (18% without AC vs. 29% with AC, OR=1.89, p=0.004), worse OS (HR=1.9, log-rank p=0.027) and worse relapse-free survival (HR=1.9, p=0.001).
Conclusions
Patients with localized AA have a low risk of relapse and an excellent prognosis. Many high-risk features derived from CRC were not associated with risk of relapse in AA, suggesting data from CRC should not be used to guide treatment decisions in AA. This retrospective analysis did not identify any benefit from adjuvant chemotherapy.
Legal entity responsible for the study
The authors.
Funding
This work was supported by the Colonel Daniel Connelly Memorial Fund, the National Cancer Institute (grant No. K22 CA234406 to Dr Shen, Cancer Center Support grant No. P30 CA016672), the Cancer Prevention and Research Institute of Texas (CPRIT) (grant No. RR180035 to Dr Shen, who is a CPRIT Scholar in Cancer Research), and a Conquer Cancer Career Development Award (to Dr Shen).
Disclosure
All authors have declared no conflicts of interest.