A new functional parameter measured at the time of ablation that can be used to predict differentiated thyroid cancer recurrence during follow-up.
BACKGROUND
This study addresses the questions whether patients with a high risk for recurrent thyroid cancer can be identified at initial stage, i.e. at the time of ablation.


METHODS
We evaluated tumor recurrence in consecutive patients treated for differentiated thyroid cancer (DTC). Prognostic factors were statistically analyzed. We defined prognostic parameters based on thyroglobulin (Tg) levels, 24-h I-131 uptake rates and TSH values: (a) Tg/TSH, (b) Tg/24-h I-131 uptake value, and (c) Tg/(TSHx24-h I-131 uptake).


RESULTS
We included 190 patients (50 male, 140 female; mean age 47 years) with DTC for analysis, 146 without distant metastases and 44 with M1 tumor stage at initial presentation. The mean period of follow-up was 10.4 years (s.d. +/- 3.7 years). In 18 out of the 146 DTC patients with M0 disease (12.4%), tumor recurrence was found during follow-up. Although tumor stage, age, and standard biochemical values significantly differ between patients with and without recurrent disease or between patients with M0 and M1 tumor stage, the newly defined parameter Tg/(TSHx24-h I-131 uptake) was the best independent significant prognostic parameter in the assessment whether patients will develop a tumor recurrence during follow-up or not.


CONCLUSIONS
High Tg/(TSHx24-h I-131 uptake) ratios justify an adjustment of the I-131 activity for ablation therapy. To assess the optimal cut-off value for a dose adjustment, however, further studies are required in more patients, but the initial results are encouraging with respect to improving outcome in DTC patients.
Verkooijen
Robbert B T
RB
Department of Nuclear Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.
Rietbergen
Daphne
D
Smit
Jan W
JW
Romijn
Johannes A
JA
Stokkel
Marcel P M
MP
D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests; D011379:Prognosis; D013268:Stimulation, Chemical; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D013972:Thyrotropin / Q000097:blood*
D007457:Iodine Radioisotopes; D013972:Thyrotropin; D013954:Thyroglobulin