Abstract
2065
Objectives This study was to evaluate clinical outcome of I-131 therapy with retinoic acid (RA) in patients with radioiodine-refractory papillary thyroid carcinoma.
Methods Nine patients (45.3 ± 10.9 yr, M:F=4:5) were treated with RA (1-1.5 mg/kg daily for 6 weeks) and followed by I-131 administration (9.7 ± 2.1 GBq). Serum stimulated thyroglobulin (Tg) level was measured before, just after, and 6 months after RA therapy, respectively. Therapeutic response was determined by change of serum Tg level and tumor size on PET/CT or radiologic exam 6 months after completion of I-131 therapy with RA. The differences of serum Tg level and radioiodine uptake on the therapeutic whole body scan (Tx-WBS) were compared before and after RA therapy.
Results Five out of 9 patients (55.6 %) showed significant decrease (above 60%) of serum Tg level on 6 months after completion of I-131 therapy with RA compared to the baseline. 3 patients showed stable disease and remaining 1 showed progressive disease. Serum Tg level just after RA therapy decreased in 4 responders (-53.5± 24.5%) except one responder. Among nonresponders, the serum Tg level just after RA therapy decreased in two patients (-20.1 and -34.7%, respectively), whereas significantly increased in two patients (117.3 and 329.3%, respectively). Tx-WBS after RA therapy could not find new metastatic lesion in all patients.
Conclusions The response rate of I-131 therapy with RA was 55.6%. RA therapy tended to decrease serum Tg level, and failed to restore radioiodine uptake. This study might support that the therapeutic effect of RA seems to be mediated by a different manner other than redifferentiation