Decreased cancer risk in patients who have been operated on with total hip and knee arthroplasty for primary osteoarthrosis: a meta-analysis of 6 Nordic cohorts with 73,000 patients.

3 Nordic cohorts of total hip (THA) and total knee arthroplasty (TKA) in patients operated on for primary osteoarthrosis during 1967-1995 were partly adapted and combined for meta-analysis. THA was performed in 49,000 patients and TKA in 24,000 totaling 497,000 person years. The mean and maximum follow-up times were 6.8 and 30 years, respectively. Standardized incidence ratios (SIRs) with 95% confidence intervals (95% CI) were calculated for the observed and expected number of cancers. The expected numbers were based on national incidence rates. The overall SIRs as well as the site-specific ones were similar in the THA and TKA patients. The observed number of cancers at all sites was 7,639 and the expected one was 8,202 (SIR 0.93, 95% CI 0.91-0.95). The SIRs for lung cancer (0.69, 0.64-0.75) and laryngeal cancer (0.64, 0.44-0.92) were reduced. The incidence was also low for cancers of the stomach (SIR 0.76, 0.67-0.84), colon (SIR 0.86, 0.79-0.93) and rectum (SIR 0.89, 0.80-0.98). Among TKA patients, the only increases in SIRs were seen in cancers of the endometrium (SIR 1.36, 1.05-1.74), prostate (SIR 1.19, 1.02-1.38) and, among both THA and TKA patients, in skin melanoma (combined SIR 1.21, 1.03-1.41).