Post-operative chemotherapy improves the survival of patients with well differentiated widespread metastatic appendiceal non-mucinous adenocarcinomas.

BACKGROUND

Appendiceal adenocarcinoma is a very rare type of tumor, often asymptomatic in the early stages of development. Surgical resection is the most preferred intervention against appendiceal non-mucinous adenocarcinoma, but the efficacy of post-operative adjuvant chemotherapy is still unclear because the cancer is rare. Accordingly, we sought to characterize appendiceal non-mucinous adenocarcinoma profile that confers a better survival advantage for post-operative chemotherapy.

METHODS

We analyzed patients with appendiceal non-mucinous adenocarcinoma in the Surveillance, Epidemiology and End Results database, histologically diagnosed for the cancer between 2004 and 2015. Nearly half of the patients first underwent surgery and thereafter received post-operative chemotherapy. Logistic regression, Kaplan-Meier, univariate and multivariate Cox analysis were performed to evaluate the odds ratio for the propensity of patients underweening chemotherapy, whereas hazard ratios were used to evaluate the overall as well as cancer-specific survival.

RESULTS

Of the 724 patients with appendiceal non-mucinous adenocarcinoma who underwent surgery, 301 (41.6%) received post-operative chemotherapy. Notably, patients with metastatic appendiceal non-mucinous adenocarcinoma were more likely to receive chemotherapy (OR =7.42, 95% CI: 5.34-10.39, P<0.001), similar to those with poor pathologically differentiated cancer types (OR =2.10, 95% CI: 1.49-3.00, P<0.001). However, univariate and multivariable Cox regression analyses found no significant overall survival and cancer-specific survival advantage for patients put on postoperative post-operative chemotherapy. In the disease stage and pathological differentiation groups, only patients with widespread metastatic (Stage IV) but well differentiated tumors displayed better 3-year (11.9% in overall survival, 11.5% in cancer-specific survival) and 5-year survival rate (7.8% in overall survival, 6.8% in cancer-specific survival) to post-operative chemotherapy.

CONCLUSIONS

Staging and grading of appendiceal non-mucinous adenocarcinoma is invaluable in guiding the rationale of post-operative chemotherapy. Findings of this research support the view that only patients with both of widespread metastatic but well differentiated appendiceal non-mucinous adenocarcinoma should be considered for post-operative chemotherapy. Nonetheless, further prospective multidisciplinary clinical trials are necessary to further discern the use chemotherapy after surgery in appendiceal non-mucinous adenocarcinoma patients.