PM13 - Treatment Variation and Long-Term Outcomes of Appendiceal Neoplasms

Background: The nomenclature used to describe Appendiceal Neoplasms has been heterogeneous and created undertainty regarding appropriate treatment. After a recent consensus, the term Low Grade Appendiceal Neoplasm (LAMN) has been widely adopted. However, we hypothesize that there is still significant variation in how LAMNs are treated and that the natural history of LAMNs is poorly understood.

Methods: We retrospectively reviewed a prospectively maintained Appendiceal registry, identifying patients with LAMNs from 2009-2019. We assessed variability in treatment patterns, including whether pts underwent colectomy; spread of disease at time of presentation; and long-term outcomes.

Results: 136 pts were identified: 90 (66%) with localized disease and 46 (34%) with disseminated peritoneal disease. Median follow-up was 2.9 yrs (IQR 1.9-4.4). 88% of pts underwent surgery prior to referral to our institution. 65 pts underwent colectomy. 46% of these were performed for perceived oncologic need/nodal evaluation; no nodal metastases were identified. In pts with resected LAMNS and no radiographic evidence of disseminated disease, 40% were offered diagnostic laparoscopy (DL) to evaluate for occult metastases. DL did not identify peritoneal disease in any of these cases. Pts presenting with disseminated disease were treated with cytoreductive surgery/heated intraperitoneal chemotherapy (CRS/HIPEC); 50% of these pts were found to have peritoneal deposits of metastatic adenocarcinoma on final pathology. For pts undergoing CRS/HIPEC, 5 yr recurrence-free survival was 94% (95% CI 81-98%); there was one disease-related death. For pts with localized disease, 5 yr RFS was 98% (85-99%).

Conclusions: There is significant variation in treatment patterns for LAMNs, particularly for patients treated prior to referral to a high-volume center. Pts frequently underwent colectomy without apparent oncologic benefit. In the current era of high-quality cross sectional imaging, routine use of DL has low yield and is not recommended. Recurrence in this population is rare and low-intensity surveillance can be offered. Overall prognosis for patients with LAMNs is excellent, even when presenting with peritoneal disease.