Appendectomy during childhood and adolescence and the subsequent risk of cancer in Sweden

Objective. Researchers have speculated that surgical excision of lymphoid tissue, such as appendectomy, early in life might confer an increased risk of cancer. In this study, we determined the risks of cancer for people who had appendectomy performed during childhood. Methods. We studied the risk of cancer in a large Swedish cohort of children who had appendectomy performed during the period of 1965-1993. Standardized incidence ratios (SIRs) were computed using age-, gender, and period-specific incidence rates derived from the entire Swedish population as comparison. Hospital discharge diagnosis data were used to examine cancer risks by categories of surgery, medical conditions, and type of appendicitis. The average length of follow-up was 11.2 years. Results. We found no excess overall cancer risk but noted a significant excess for stomach cancer (SIR: 2.45; 95% confidence interval [CI]: 1.1-4.8) and a borderline increase of non-Hodgkin's lymphoma (NHL; SIR: 1.55; 95% CI: 1.0-2.3). The elevated risks for both cancers were only evident 15 or more years after appendectomy (stomach cancer, SIR: 3.82; 95% CI: 1.7-7.5; NHL, SIR: 2.49; 95% CI: 1.4-4.2). Conclusions. It is reassuring that there was no overall increase of cancer several years after childhood appendectomy. Increased risks for NHL and stomach cancer, occurring 15 or more years after appendectomy, were based on small absolute numbers of excess cancers. As 95% of the subjects were younger than 40 years at exit, this cohort requires continuing follow-up and monitoring.