Abstract
BACKGROUND & AIMS: Cancer risk after appendectomy in patients with appendicitis remains unclear. This study examined the role of appendicitis as an early manifestation harbingering the distant malignancy. METHODS: From the insurance claims data of Taiwan, we identified a cohort of 130,374 patients newly received appendectomy from 2000-2009, without cancer diagnosis. A comparison cohort of 260,746 persons without appendectomy and cancer was selected from the same database, frequency matched by age, sex, comorbidity and index year. We monitored subsequent cancers with a12-month follow-up. RESULTS: Over all, 1406 and 616 cancer cases were identified in the appendectomy cohort and comparisons, respectively, with all cancers incidence rate 4.64-fold higher in the appendectomy cohort (9.06 vs. 1.96 per 1000 person-months). Digestive and female genital organs harbored 80.9% of cancer cases in the appendectomy cohort. The Cox model measured site-specific hazard ratio (HR) was the highest for female genital cancers (23.3), followed by cancers of colorectum (14.7), small intestine (10.1), pancreas (7.40), lymphoma (5.89) and urinary system (4.50), all significant at 0.001 level. The HR of all cancers decreased from 13.7 within 3 months after appendectomy to 1.37 in 7-12 months after the surgery. In general, relative to the comparison cohort, younger appendectomy patients tended to have a higher HR than older patients. CONCLUSIONS: The high incident cancers identified soon after appendectomy suggest the acute appendicitis is the early sign of distant metastatic malignancy. The risk of colorectal cancer, female genital cancer and haemopoietic malignancy deserve attention.