The value of detectable thyroglobulin in patients with differentiated thyroid cancer after initial ¹³¹I therapy.

OBJECTIVE: To assess the prognostic value of detectable thyroglobulin (Tg) after initial surgery and radioactive iodine (¹³¹I) therapy by comparing patients with a negative post-therapeutic whole body scan (WBS) with either detectable or undetectable Tg. BACKGROUND: Differentiated thyroid cancer has a good prognosis. However, recurrences can occur up to 30 years after initial treatment. Because life-long follow-up is necessary, it is important to explore possible risk factors associated with recurrence and mortality. DESIGN, PATIENTS AND MEASUREMENTS: We studied 539 patients who were treated between 1980 and 2007. After the last therapeutic dosage of 5550 MBq ¹³¹I, 72 patients had negative post-therapeutic WBS and positive Tg levels (Tg+ group) and 399 patients had negative post-therapeutic WBS and negative Tg (Tg- group). The 68 remaining patients had proven residual macroscopic disease. We investigated recurrences and overall mortality in the Tg+ and Tg- group compared with the Dutch population. RESULTS: In the Tg+ group, detectable recurrences occurred significantly earlier and more frequently than in the Tg- group (19%vs 13%, P = 0·024). Survival between these groups was comparable, but shorter than the general Dutch population [Standardised Mortality Rate (SMR) 1·38 (95% CI 1·12;1·63) (P = 0·003)]. Disease-free survival in the Tg groups was comparable and not significantly different from the Dutch population [SMR = 1·09 (95% CI 0·81;1·34) (P = 0·569)]. CONCLUSION: Patients with detectable Tg during the last ¹³¹I treatment and a negative post-therapeutic WBS have significant earlier and more recurrences than patients without detectable Tg. Survival in both groups is comparable. After initial therapy, the combination of a negative high dose post-therapeutic WBS with detectable Tg is a valuable predictor for earlier and more recurrences, but is not associated with survival.