Twenty-seven studies were included in the review, 20 of which were included in the previous systematic review. All studies were cohort studies. Where reported, median follow-up ranged from five to 21.4 years. Seventeen studies reported the treatment effect of RAA after statistical adjustment for prognostic factors. RAA was associated with a significant reduction in the risk of thyroid cancer related mortality.
There were no additional unadjusted data on thyroid cancer mortality data; therefore, the authors reported the results of the analysis conducted in their previous review (see Other Publications of Related Interest), namely that there was a high degree of statistical heterogeneity between the 16 included studies (n=6,464, Χ2=27.44, p=0.025). Ten-year incidence of thyroid cancer mortality in the five studies of papillary patients only was estimated to be 1.7% (n=2,627).
Unadjusted analyses for the outcome of any recurrence (present review): There was statistically significant heterogeneity (n=5,307, Χ2=122.71, p<0.00001, I2=91%) and loco-regional recurrence (n=1,244, Χ2=20.36, p=0.001, I2=75%). RRA was associated with a statistically significantly reduced risk of distant metastasis (RD -2%, 95% CI -4% to -1%, I2=0%; n=2,263).