Histological Subtype Remains a Significant Prognostic Factor for Survival Outcomes in Patients With Appendiceal Mucinous Neoplasm With Peritoneal Dissemination.

BACKGROUND: It has been increasingly recognized that appendiceal mucinous neoplasm with peritoneal dissemination is not a homogenous disease.

OBJECTIVE: This study aimed to examine the impact of different histological subtypes on survival of a large cohort of patients with appendiceal mucinous neoplasms uniformly treated by cytoreductive surgery and intraperitoneal chemotherapy.

DESIGN: This was a retrospective study of prospectively collected data of patients with peritoneal dissemination of appendiceal neoplasm who underwent cytoreductive surgery and intraperitoneal chemotherapy.

SETTING: The study was conducted by 1 surgical team at St. George Hospital.

PATIENTS: A total of 444 patients formed the cohort of this study.

MAIN OUTCOME MEASURES: Histological diagnoses were categorized based on Carr criteria to include acellular mucin, disseminated peritoneal adenomucinosis, peritoneal mucinous neoplasms without signet ring cells, and peritoneal mucinous carcinomatosis with signet cells.

RESULTS: Patients with low-grade appendiceal mucinous neoplasms with neoplastic epithelium absent tended to have lower CEA, CA19-9, and CA125 levels preoperatively (p = 0.109, 0.008, and 0.034). Factor analysis showed that histological diagnosis was an independent prognostic factor for survival outcomes (HR = 3.13 (95% CI, 2.34-4.39); p < 0.001), adjusted for peritoneal cancer index >20, completeness of cytoreductive score ≥2, use of early postoperative intraperitoneal chemotherapy, transfusion units, CEA >7.0 mg/L, CA19-9 >24.0 U/mL, and CA125 >24 U/mL.

LIMITATIONS: This study was limited by its retrospective nature, lack of uniform classifications of appendiceal mucinous neoplasms in early years, and the heterogeneity of this study cohort given the long study period.

CONCLUSIONS: Histological subtype remains a significant prognostic factor for survival outcomes in patients with appendiceal mucinous neoplasms. It should be taken into account when selecting patients for cytoreductive surgery, tailoring appropriate adjuvant therapies and follow-up surveillance plan.