E344: Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy in Management of Appendix Cancer with Peritoneal and Parenchymal Metastases: the National Cancer Database Analysis

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) improve survival in patients with appendix cancer and peritoneal carcinomatosis (PC). Its role in patients with both peritoneal and parenchymal metastases remains unclear. We aimed to assess outcomes of CRS/HIPEC in stage IVC mucinous (MAC) and non-mucinous AC (N-MAC).

Methods:

A multicenter retrospective cohort study was conducted using the National Cancer Database (2004-2019). MAC, N-MAC, and signet ring cell carcinoma patients with PC and liver and/or lung metastasis were included. Overall survival (OS) was compared between patients who received CRS/HIPEC, CRS without HIPEC, and only systemic chemotherapy (SCT). Cox regression analysis with adjustment to age, sex, insurance, co-morbidities, histology, and metastasis site was performed.

Results:

Out of 42,888 patients, 950 met the inclusion criteria: 186 received CRS/HIPEC, 586 – CRS, and 196 – SCT. Median age was 58 vs 59 vs 60 years in CRS/HIPEC, CRS, and SCT groups, respectively (p=0.02). CRS/HIPEC was more commonly performed in academic settings (54.3% vs 36.4% vs 43.9%, p< 0.01), in patients with private insurance (63.4% vs 51.8% vs 61.2%, p< 0.01), and in mucinous histology (88.2% vs 48.1% vs 46.4%, p< 0.01). Liver metastases were more common in CRS/HIPEC than in CRS or SCT groups: 96.2% vs 80.5% vs 64.3% whereas lung metastases were more common in SCT: 2.7% vs 12.1% vs 22.4% (p< 0.01). CRS/HIPEC patients received pre- and/or postop systemic chemotherapy less often than CRS patients (33.9% vs 73.1%, p< 0.01).

Median follow-up was 58 (95%CI 54.8-61.2) months. Among all patients, median OS was not reached (NR) in CRS/HIPEC, 22 months in CRS, and 15 months in the SCT group (p< 0.01). OS differed significantly between CRS/HIPEC, CRS, and SCT groups in low-grade MAC (NR vs 50 vs 26 months, p< 0.01) and low-grade N-MAC (NR vs 20 vs 6 months, p< 0.01) and there was no difference in OS in high-grade MAC (35 vs 13 vs 13 months, p=0.30) and high-grade N-MAC (9 vs 10 vs 3 months, p=0.22). In patients with liver metastases, the median OS was longer in CRS/HIPEC: 94 vs 25 vs 15 months, respectively (p< 0.01).
CRS/HIPEC (SCT ref.; HR 0.36; 95%CI 0.26-0.50) and CRS (HR 0.69; 95%CI 0.57-0.85) were associated with longer OS when adjusted to other factors.

Conclusions: Selected low-grade MAC and N-MAC patients with PC and parenchymal metastases can benefit from CRS/HIPEC. Larger studies are needed to assess its efficacy in patients with stage IVC high-grade appendix cancer.