Abstract
The objective of the work was to investigate the relationship between thyroglobulin
doubling time (TgDT) as a marker of speed of response to 131I-therapy and the differentiated thyroid cancer (DTC) recurrence rate, DTC specific
mortality rate, and relative survival rate in a DTC population followed over a long
period of time after 131I-therapy. From our database, data of 1354 patients were reviewed. TgDT could be calculated
in 174 patients, however, 376 patients did not have sufficient Tg values available
for TgDT calculation and 804 patients reached biochemical remission before a sufficient
number of Tg measurements for TgDT calculation was acquired. Main outcome measures
were recurrence-free, DTC specific, and relative survival rates. In patients<45 years,
TgDT in multivariate analysis was identified as the solitary significant determinant
of DTC specific and relative survival. In patients≥45 years of age at diagnosis, TgDT
is an independent, but not the only determinant of recurrence free, DTC specific,
and relative survival. Importantly, in this age group life expectancy is normal in
patients reaching rapid biochemical remission (i. e., before TgDT can be calculated);
it was reduced in patients with a negative TgDT, which normally is deemed a marker
of response to therapy. Only DTC patients with a rapid biochemical remission have
a very good prognosis with a normal life expectancy. If no rapid biochemical remission
occurs, both biochemically progressive disease and a slower biochemical remission
of disease are associated with a reduced prognosis, especially in older DTC patients.
Key words
differentiated thyroid carcinoma - thyroglobulin - thyroglobulin doubling time - prognosis
- life expectancy
