The role of systemic chemotherapy in adenocarcinomas of the appendix: Analysis of the National Cancer Database.

Abstract

668 Background: Adenocarcinomas of the appendix represent a heterogeneous disease depending upon the presence of mucinous histology, histologic grade, and stage. We sought to explore the interplay of these factors with systemic chemotherapy in a large population dataset. Methods: Patients in the National Cancer Data Base (NCDB) with mucinous, non-mucinous and signet-ring cell type appendiceal neoplasms from 1985-2006 were selected and American Joint Committee on Cancer (AJCC) 7thedition stage was derived. Multivariable cox proportional hazards regression models to predict death using the available variables age, sex, histology, grade, stage, chemotherapy and surgery were developed. Results: 11,881 patients met our inclusion criteria: 50.3% mucinous, 40.5% non-mucinous and 9.2% signet ring cell. 5-yr OS was similar for mucinous (53.6%) and non-mucinous (46.2%), but differences in stage distribution existed with stage IV disease in 26.2% of mucinous vs. 10.6% of non-mucinous cases, p<0.0001. 5-yr OS stratified by grade was similar across stage I-III disease but not for stage IV disease. Median OS for stage IV mucinous and non-mucinous histology was 6.4 and 2.3 for well differentiated (p<0.0001), 2.5 and 1.0 for moderately differentiated (p<0.0001), and 1.5 and 0.8 for poorly differentiated (p<0.0001), respectively. In multivariable modeling for stage I-III disease, adjuvant chemotherapy improved OS for both mucinous and non-mucinous histologies: HR of 0.78 (0.68-0.89; p=0.0002) and 0.83 (0.74-0.94;p=0.002) respectively. For stage IV disease systemic chemotherapy was significant for non-mucinous 0.72 (0.64-0.82; p<0.0001) but not mucinous 0.95 (0.86-1.04;p=0.2), though this was grade dependent. Median OS for chemotherapy vs. no chemotherapy was 6.4 vs. 6.5 yrs (P=1.0) for mucinous well differentiated and 1.6 vs. 1.0 yrs (P=0.0007) for mucinous poorly differentiated. Conclusions: Adjuvant chemotherapy demonstrated a significant OS benefit regardless of histology. However, for stage IV disease the benefit of systemic chemotherapy varied by histology and grade, with well differentiated mucinous appendiceal adenocarcinomas deriving no survival benefit from systemic chemotherapy.