Comparison between remnant and red-marrow absorbed dose in thyroid cancer patients submitted to 131I ablative therapy after rh-TSH stimulation versus hypothyroidism induced by L-thyroxine withdrawal

Nucl Med Commun. 2007 Mar;28(3):215-23. doi: 10.1097/MNM.0b013e328014a0f6.

Abstract

Objective: In thyroidectomized patients, increased levels of thyroid stimulating hormone (TSH) are necessary to maximize I uptake. Traditionally, this has been achieved by withdrawing L-thyroxine (L-T4) for 4-6 weeks, inducing hypothyroidism in patients. The availability of a genetically engineered version of the recombinant human TSH (rh-TSH) provides an alternative tool to enhance the TSH serum level without inducing hypothyroidism. In this paper the I remnant and red-marrow doses calculated in differentiated thyroid cancer (DTC) patients pre-treated with rh-TSH are compared to those calculated in patients in hypothyroidism induced by L-T4 withdrawal.

Methods: Forty-six DTC patients, submitted to I ablative therapy, were randomly divided in group A (pre-treated with rh-TSH) and group B (treated after L-T4 withdrawal for 30 days). The red-marrow absorbed dose per unit administered activity and the remnant cumulated activity per unit administered activity were calculated for both groups.

Results: The red-marrow dose in 17 rh-TSH treated patients is 0.06+/-0.02 mGy.MBq; that in 14 hypothyroid patients is 0.09+/-0.03 mGy.MBq (two-tailed unpaired t-test P=0.003). The remnant cumulated activity per unit administered activity in 10 rh-TSH treated patients is 0.9+/-0.8 h; that calculated in 21 hypothyroid patients is 1.55+/-1.05 h (two-tailed unpaired t-test P=0.063). This last result is mainly due to the difference between the maximum uptake (U) in rh-TSH (U=0.01+/-0.01) and hypothyroid patients (U=0.03+/-0.02) (two-tailed unpaired t-test P=0.019).

Conclusion: The rh-TSH pre-treated patients seem to have a lower uptake compared to those in hypothyroidism induced by L-T4 withdrawal. On the other hand their red-marrow absorbed dose seems to be lower.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Bone Marrow / diagnostic imaging*
  • Bone Marrow / metabolism*
  • Female
  • Humans
  • Hypothyroidism / diagnostic imaging*
  • Hypothyroidism / etiology
  • Iodine Radioisotopes / therapeutic use*
  • Male
  • Middle Aged
  • Radiometry
  • Radionuclide Imaging
  • Recombinant Proteins / therapeutic use
  • Substance Withdrawal Syndrome / diagnostic imaging*
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Neoplasms / radiotherapy*
  • Thyroidectomy
  • Thyrotropin / therapeutic use*
  • Thyroxine / adverse effects*
  • Thyroxine / therapeutic use

Substances

  • Iodine Radioisotopes
  • Recombinant Proteins
  • Thyrotropin
  • Thyroxine