Abstract
This study aimed to compare mucinous carcinoma and adenocarcinoma of the appendix in terms of survival and investigate the risk factors influencing survival. The data for this study were retrieved from the SEER database (SEER Research Plus 17 registries). Patients diagnosed with appendix cancer between 2004 and 2019 were included. Demographic data, such as age, gender, marital status, and year of diagnosis, along with oncological variables like stage, surgery, chemotherapy, radiotherapy, and survival time, were extracted from the SEER database. Pathological subtypes were classified as adenocarcinoma (AC) and mucinous adenocarcinoma (MAC) based on the College of American Pathologists guidelines. Patients with other pathological subtypes or missing data were excluded from the study. This study included 4524 patients, with 2118 (46.8%) classified as AC and 2406 (53.2%) as MAC. There was no significant difference in mean age between AC and MAC groups (63.22 ± 14.30 vs. 59.46 ± 14.07, p = 0.483). AC was more common in males, while MAC was more prevalent in females (46.8% vs. 53.2%; 55.6% vs. 44.4%, p < 0.001, respectively). Married status was high in both groups (p = 0.001). While no difference was found in white race distribution, the black race was more prevalent in the AC group (57.1% vs. 42.9%, p < 0.001). Grade 1 tumors were more frequent in the AC group, whereas Grades 2 and 3 were more common in the MAC group (p < 0.001). Stages 1, 2, and 3 were more prevalent in the AC group, while the majority of MAC cases were at Stage 4. Surgery rates were higher in the AC group (98.6% vs. 96.4%, p < 0.001). Chemotherapy was used more frequently in the MAC group (50.9% vs. 40.6%, p < 0.001), while radiotherapy rates were similar in both groups (p = 0.498). The mean follow-up period was 55.70 ± 47.2 months. Five- and ten-year survival rates for the MAC group were 64.4% and 50.2%, respectively, higher than the AC group's rates of 54.2% and 39.7% (p < 0.001). The overall risk of mortality was 1.4 times higher in the AC group compared to the MAC group (p < 0.001, HR: 1.377 [CI 95% 1.259-1.507]). While adenocarcinomas and mucinous adenocarcinomas have similar incidences, non-metastatic adenocarcinomas were more frequently observed. In contrast, mucinous adenocarcinomas often exhibited distant metastases. Nevertheless, the survival rate was higher in mucinous adenocarcinomas.