Chemotherapy in the treatment of different histological types of appendiceal cancers: a SEER based study

Background Due to its rarity and high heterogeneity, neither established guidelines nor prospective data are currently available for using chemotherapy in the treatment of appendiceal cancer. This study was to determine the use of chemotherapy and its potential associations with survival in patients with different histological types of the cancer. Methods Patients with histologically different appendiceal cancers diagnosed during 1998–2016 were selected from the Surveillance, Epidemiology, and End Results (SEER) database. The role and effect of chemotherapy were examined in the treatment of the disease. The Kaplan-Meier method was applied to construct survival curves and significance was examined by Log-rank test. Cox proportional hazard models were used to analyze the impact of chemotherapy and other variables on survival in these patients. Results A total of 8733 appendiceal cancer patients were identified from the database. Chemotherapy was administrated at highly variable rates in different histological types of appendiceal cancer. As high as 64.0% signet ring cell carcinoma (SRCC), 46.4% of mucinous adenocarcinomas (MAC), 40.6% of non-mucinous adenocarcinoma (NMAC) and 43.9% of mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) were treated with chemotherapy, whereas only 14.7% of goblet cell carcinoma (GCC), 5% neuroendocrine tumors (NETs) and 1.6% carcinomas (NEC) received chemotherapy. In all patients combined, chemotherapy significantly improved overall survival during the entire study period and cancer-specific survival was improved during in cases from 2012–2016. Further multivariate analysis showed that both cancer-specific and overall survival was significantly improved with chemotherapy in patients with MAC, NMAC and SRCC, but not for patients with GCC, MiNENs, NETs and NECs. Number (> 12) of lymph node sampled was associated with survival of patients with most histological types of cancer under study. Other prognostic factors related to individual histological types were identified. Conclusions Chemotherapy is administrated at highly variable rates in different histological types of appendiceal cancer. Efficacy of chemotherapy in the treatment of these cancers has been improved in recent years and is significantly associated with better survival for patients with NMAC, MAC, and SRCC. Adequate lymph node sampling may result in a survival benefit for most of these patients.