Low-grade Appendiceal Mucinous Neoplasm of Uncertain Malignant Potential (LAMN-UMP): Prognostic Factors and Implications for Treatment and Follow-up.

BACKGROUND

Low-grade appendiceal mucinous neoplasm of uncertain malignant potential are poorly understood lesions characterized by extraluminal mucin or fibrosis with neoplastic cells confined to the appendiceal lumen. The purpose of this study is to investigate the clinical and pathologic parameters of these lesions to optimize our understanding and management of these tumors.

METHODS

Subjects with these tumors were identified from the appendiceal tumor databases at the University of Texas MD Anderson Cancer Center. Univariate and multivariate Cox proportional hazards regression analyses assessed relationships between clinicopathologic variables [including age, gender, margin status and serum levels of the tumor markers carcinoembryonic antigen (CEA), cancer antigen (CA)-125, and CA19-9] disease-free survival, postrecurrence survival and overall survival.

RESULTS

Ninety-eight subjects with this disease were identified. Most patients did not experience disease recurrence after initial appendectomy. At last follow-up, 25 (26 %) had disease recurrence or died. Of the 20 patients who had disease recurrence, 5 (25 %) died, and 15 (75 %) were alive. Disease-free survival was significantly reduced with positive margin status (p = 0.02) and elevated serum levels of CEA (p < 0.001), CA19-9 (p = 0.01), or CA-125 (p = 0.002) at the time of appendectomy. The median postrecurrence survival time was 4.7 years and the 5-year postrecurrence survival rate was 41 % (standard error = 18 %).

CONCLUSIONS

Patients with Low-grade appendiceal mucinous neoplasm of uncertain malignant potential who have negative margins and normal tumor marker levels have a lower risk for recurrence. In these patients, expectant management is sufficient. Elevated tumor marker levels at the time of appendectomy marks an increased risk of recurrence or death and signals the need for closer monitoring or intervention.