A nationwide population-based cohort study on tonsillectomy and subsequent cancer incidence.

OBJECTIVES/HYPOTHESIS Tonsillectomy is related to increased risk of certain types of cancer. This study evaluates the possible association between tonsillectomy and cancer in Taiwan. METHODS Data from the National Health Insurance system of Taiwan was used. A cohort study consisting of 997 patients with a new diagnosis of tonsillectomy from 2000 to 2005 and a comparison cohort of 3,988 subjects without tonsillectomy were used in the Poisson regression analysis to estimate the incidence rate ratios (IRRs) and 95% confidence intervals (CIs) of cancers. RESULTS The incidence rate of all cancer types was higher in the tonsillectomy group than in the control group (4.28 vs. 2.97 per 1,000 person-years, respectively), with an IRR = 1.54 and 95% CI of 1.05 to 2.25, but the significant difference was limited to patients with more than 3 years follow-up. Site-specific analysis found no significant association between tonsillectomy and any individual cancer after adjusting for age, sex, hyperlipidemia, hypertension, and diabetes; however, tonsillectomy patients with more than 3 years follow-up had a marginally significantly higher risk for breast cancer development (adjusted IRR = 2.62; CI = 0.97-7.03). CONCLUSION Our study found that Taiwanese people with tonsillectomy have a significantly higher overall risk of developing cancer and a marginally higher risk of developing breast cancer when follow-up is longer than 3 years.