Retrospective study of nonmucinous appendiceal adenocarcinomas: role of systemic chemotherapy and cytoreductive surgery.

Background: Mucinous appendiceal adenocarcinomas (AAs) are the most common histological subset of AAs. Nonmucinous AAs have been infrequently studied. We performed a single-center retrospective study to investigate this histological subtype.

Methods: We reviewed 172 patient records with nonmucinous AAs treated at MD Anderson Cancer Center from Jan, 1990 to Jun, 2015 and recorded patient demographics, tumor characteristics, treatment, and outcomes. Response rate (RR) was assessed semi-quantitatively (response/no response) according to the treating physician's findings. Survival outcomes were calculated using the Kaplan-Meier product-limit method and compared using the log-rank test.

Results: Median age at diagnosis was 52.9 years. Most patients presented with advanced-stage disease: stage I-II (35%), stage III (15%), and stage IV (50%). Moderate and poorly differentiated histology was seen in 56% and 44% tumors, respectively. Median overall survival (OS) of all patients was stage-dependent and was 88.5, 39.2, and 28.3 months for stages I-II, stage III, and stage IV disease, respectively (p < 0.0001). In patients with metastatic disease, only 10% had extraperitoneal disease without peritoneal involvement. Cytoreductive surgery (CRS) was attempted in 31/69 (45%) patients with disease confined to the peritoneum. Complete CRS was achieved in 18. Median OS for patients receiving complete CRS was 48.6 months. Systemic chemotherapy was administered to 109 (86%) patients with metastatic disease; a large majority of patients received either an oxaliplatin-based (55%) or irinotecan-based (27%) regimen. Chemotherapy resulted in a semi-quantitative RR of 54% and median time to progression (TTP) of 9.4 months (95% CI, 8.03-11.50). Patients who received combination chemotherapy (either oxaliplatin or irinotecan-based) showed significantly longer median OS (p = 0.003), compared to those receiving fluoropyrimidine monotherapy.

Conclusions: This is one of the first studies to report specifically on nonmucinous AAs. Nonmucinous AAs presented with moderate or poorly differentiated histology with a predilection for peritoneal metastasis. Systemic chemotherapy is active in this AA subtype. Though CRS was infrequently used, complete CRS appears beneficial and warrants further investigation.