Ultrasensitive serum thyroglobulin measurement is useful for the follow-up of patients treated with total thyroidectomy without radioactive iodine ablation

Abstract

Thyroglobulin (Tg) measurement is a major tool for the follow-up of differentiated thyroid cancer (DTC) patients; however, in patients who do not undergo radioactive iodine (RAI) ablation, normal ultrasensitive Tg levels measured under levothyroxine treatment (usTg/l-T4) are not well defined. This single-center retrospective study assessed usTg/l-T4 level in 86 consecutive patients treated with total thyroidectomy without RAI ablation for low-risk DTC (n=77) or for tumors of uncertain malignant potential (TUMP) (n=9). DTCS were classified as PT1, PT2, and PT3 in 75, 1, and 1 case respectively and PN0, PN1, and PNX in 40, 6, and 31 respectively. following surgery, ten patients had TG antibodieS (TGAB). Among those without TGAB, the first USTG/L-T4 determination obtained at a mean time of 9 months after surgery was 0.1NG/ML in 62% of cases, 0.3NG/ML in 82% of cases, 1NG/ML in 91%, and 2NG/ML in 96% of cases. after a median follow-up of 2.5 years (range: 0.6-7.2 years), one patient had persistent disease with an usTg/l-T4 at 11 ng/ml and an abnormal neck ultrasonography (US) and two patients had usTg/l-T4 level >2 ng/ml (3.9 and 4.9 ng/ml) with a normal neck US. Within the first 2 years following total thyroidectomy without RAI ablation, usTg/l-T4 level is ≤2 ng/ml in 96% of the cases. After total thyroidectomy, sensitive serum Tg/l-T4 level is ≤2 ng/ml in most patients and can be used for patient follow-up.