Study rationale
High risk patients with differentiated thyroid cancer (DTC) require therapy with 131 I under thyroid stimulating hormone (TSH) stimulation. There are two methods of TSH stimulation endogenous by thyroid hormone withdrawal (THW) leading to hypothyroidism and exogenous by injection of human recombinant TSH (rhTSH Thyrogen). The appropriate 131-I activity utilized for treatment is either based on empiric fixed dosage choice or individually determined activity based on 131 I dosimetric calculations. Although dosimetry utilizing radioactive iodine isotope 131 I enables calculation of maximum safe dose, it does not estimate the tumoricidal activity necessary to destroy the metastatic lesions. The alternative radioactive isotope of iodine -124 I, used for positron emission tomography (PET) imaging, might be used for calculation not only the maximum safe131 I dose, but also to predict the absorbed dose in the metastatic lesions.
Study objectives
The primary objective of this study is to compare the 124 I -PET/CT lesional and whole body dosimetry in each individual patient with metastatic radioiodine (RAI)-avid thyroid cancer under preparation with rhTSH and THW. The secondary objective is to evaluate the predicted by PET/CT lesional uptake with the early response to therapy.
Study design
This is a phase 2 pilot prospective cohort study comparing the lesional and whole body dosimetry within each patient undergoing exogenous (rhTSH) and endogenous (THW) TSH stimulation and followed for 5 years.
Interventions
Each study participant will undergo rhTSH and THW-aided 124 I-PET/CT dosimetric evaluations and will be subsequently treated with THW-aided RAI activity based on dosimetric calculations enabling maximum safe dosage. The patients will be followed in 12+/-3 months intervals for 5 years.
Sample size and population
This pilot study will include 30 patients with high risk differentiated thyroid cancer presenting with distant and/or loco-regional metastases.
underwent total thyroidectomy plus or minus neck lymph node dissection as clinically indicated,
are presenting with known per structural imaging (US neck, CT or MRI neck/chest/abdomen/pelvis) persistent/recurrent disease either locally advanced or presenting with distant metastases; or
are presenting with suspected persistent/recurrent locoregional or distant metastases based on the high risk features such as advanced tumor per pathology report (tumor size >4 cm, exrathyroidal extension, higher risk pathology such as tall cell, columnar cell, poorly differentiated variant, follicular thyroid cancer with gross vascular invasion, positive margins after the surgery, bulky lymphadenopathy in the central and/or lateral neck), detectable/increasing baseline/suppressed thyroglobulin (Tg) level or detectable/increasing anti-Tg antibody titers if anti-Tg antibodies are present.
are either RAI -naive or requiring repeated RAI therapy for locally advanced disease or distant metastases or underwent therapy with BRAF inhibitor (dabrafenib or vemurafenib*) or selumetinib** for at least 4 weeks that may re-induce RAI uptake.
Serious underlying medical conditions that restrict diagnostic testing or therapy such as renal failure, congestive cardiac failure or active coexisting non-thyroid carcinoma, severe depression which might be exacerbated by thyroid hormone withdrawal.
Patients with spinal or brain metastases as they are at risk of TSH-stimulation induced swelling of metastatic lesions leading to potentially detrimental side effects. These patients will be evaluated per the standard of care protocol 77-DK-0096.
Pregnant or lactating women per self report.
Adults who are incapable of providing informed consent.
Crossover
Thyrogen
Drugintramuscular injection administered once/day for 2 consecutive days at Week 3; then once annually for subjects who meet criteria.
I-131
Radiationtherapeutic dose administered orally to treat thyroid cancer at Week 8. 5-7 days later, the post-treatment I-131 Whole Body scan w/ SPECT is performed; then administered once annually, if the patient needs to be re-treated
I-124
Radiationone capsule ingested orally once at Week 3, and Week 8; then administered once annually to subjects who meet criteria.
Thyroid hormone withdrawal
Other interventionwithdrawal of thyroid hormone during weeks 4 through 8
Comparison of the whole body and lesional 124I uptake within each patient prepared for imaging with human recombinant TSH (rhTSH) and thyroid hormone withdrawal (THW)
Whole body and lesional uptake of 124I calculated after preparation with human recombinant TSH (rhTSH) compared to dosimetry calculated after preparation using thyroid hormone withdrawal (THW)
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