O3029 CANCER INCIDENCE AFTER TOTAL KNEE ARTHROPLASTY ADDITIONAL FOUR-YEAR FOLLOW-UP WITH A NATIONWIDE FINNISH COHORT INVOLVING 9,443 PATIENTS

Abstract

Aims: Nationwide, computer-based survey of all total joint arthroplasties performed in Finland has been carried out since January 1980. From these records a cohort of 9,443 patients, with 80,734 person-years, after primary operation with a total polyethylene-on-metal knee arthroplasty (TKA) has been followed up for cancer. In 1999 we published the material until December 31, 1996. The standardized incidence ratio (SIR) for all cancers was 0.98. The SIRs for non-Hodgkin lymphoma (1.40), Hodgkinñs disease (1.24), multiple myeloma (1.54) and prostate cancer (1.49) were increased, but only that of non-Hodgkin lymhoma was statistically signiþcant 3 to 10 years after the operation. The overall cancer risk after TKA done for primary osteoarthrosis appeared to be negligible. Material and methods: Follow-up for cancer was undertaken using the þles in the population-based, nationwide Finnish Cancer Registry, employing personal identiþcation numbers. Follow-up for cancer started at the date of þrst knee replacement and ended on emigration, death, or 31 December 2000, whichever occurred þrst. No subject was lost to follow-up. Standardized incidence ratios (SIRs) were calculated by dividing observed numbers of cases by expected numbers. Results: There were 2,001 men and 7,442 women left in the cohort to be followed-up. Numbers of person-years are now 15,679 and 650,552, respectively. The mean duration of follow-up per person was therefore 8,5 years. During the 21-year follow-up period, 358 cases of cancer occurred in the male subjects. The expected number was 349. In the female subjects 801 cases of cancer were observed vs. 804 expected. Combining data for men and women, the SIR for cancer at all sites was 1.00. SIRs were signiþ-cantly lower in relation to cancers of the lung (0.69), and colon (0.77). The incidence of risk of colon cancer was lower than would have been expected only in women (SIR 0.70). As far as cancers of the urinary organs is concerned, the SIR was within unity (SIR 1,03). The overall incidence of non-Hodgkin lymphoma (extranodal sites included) was elevated, but without any statistical signiþ-cance (SIR 1.22). The SIR values for multiple myeloma and leucemia have reduced to 0.80 and 0.53. Conclusions: We conclude, that this large nation-wide material could not establish any association between TKA and the all-over incidence of remote or adjacent cancers; on the contrary incidences of certain cancers were in fact lower than those reported in the formed material with four years less follow-up. All the alarming SIRs in the former material, especially those with non-Hodgin lym-phoma, urinary tract cancers and leucemia, have now reduced and are less than unity.