Recombinant Human Thyroid-Stimulating Hormone Versus Thyroid Hormone Withdrawal in 124I PET/CT–Based Dosimetry for 131I Therapy of Metastatic Differentiated Thyroid Cancer

Donika Plyku; Robert F. Hobbs; Kevin Huang; Frank Atkins; Carlos Garcia; George Sgouros; Douglas Van Nostrand

doi:10.2967/jnumed.116.179366

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FIGURE 1.
Transverse and sagittal views of patients’ CT and PET images (superimposed) and drawn VOIs covering lungs (A), heart (B), liver (C), kidneys (D), bone marrow (E), and tumor (F).
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FIGURE 2.
Activity measurement method in tumors.
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FIGURE 3.
Normal organ %IA/cm³ vs. time (hr) after injection of ¹²⁴I for rhTSH and THW for patient 1 (A), patient 2 (B), patient 3 (C), and patient 4 (D). Pt = patient.
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FIGURE 4.
Difference in time-integrated activity coefficient (THW − rhTSH)/THW.
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FIGURE 5.
Aggregate tumor and bone marrow ¹²⁴I activity concentration (%IA/cm³), rhTSH (dotted) and THW (solid) study for patient 1 (A), patient 2 (B), and patient 3 (C).

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TABLE 1

Patient Demographics

Characteristic	Patient 1	Patient 2	Patient 3	Patient 4
Age (y)	47	30	63	51
Sex	M	M	M	M
Thyroglobulin level (ng/mL)	170^*; 324^†	NA^*; 1,527^†	3,735^*; 2,480^†	86^*; 58^†
TSH level (μIU/mL)	98^*; 82.9^†	139^*; 142^†	89^*; 124^†	64^*; 72^†
Urine iodine level (μg/L)	182^‡; 85^†	75^‡; 630^†	99^‡; NA^†	28^‡; 21^†
Thyroxine dose before and during rhTSH stimulation (μg)	125	125	139	200

↵* Under rhTSH.
↵† Under THW.
↵‡ Before rhTSH.
NA = not applicable.

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TABLE 2
¹²⁴I and ¹³¹I Administered Activities
¹²⁴I activity (MBq) ¹³¹I activity
Patient no. rhTSH THW mCi MBq
1 30 29 319 11,803
2 61 65 398 14,726
3 36 33 198 7,326
4 37 33 326 12,062

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TABLE 3

Absorbed Dose per Unit Administered Activity of ¹³¹I for Each Study (rhTSH and THW) and Ratio in Absorbed Dose per Unit Administered Activity (THW/rhTSH)

	Organ VOI
Patient	Lungs	Heart	Liver	Kidneys	Bone marrow
1
Absorbed dose per unit administered activity for rhTSH (mGy/MBq)	0.21	0.15	0.15	0.19	0.13
Absorbed dose per unit administered activity for THW (mGy/MBq)	0.58	0.21	0.19	0.17	0.11
THW/rhTSH ratio	2.8	1.4	1.3	0.9	0.85
2
Absorbed dose per unit administered activity for rhTSH (mGy/MBq)	0.11	0.27	0.11	0.11	0.086
Absorbed dose per unit administered activity for THW (mGy/MBq)	0.66	0.33	0.20	0.23	0.14
THW/rhTSH ratio	6.0	1.2	1.8	2.1	1.6
3
Absorbed dose per unit administered activity for rhTSH (mGy/MBq)	0.44	0.46	0.40	0.44	0.33
Absorbed dose per unit administered activity for THW (mGy/MBq)	0.25	0.28	0.24	0.32	0.22
THW/rhTSH ratio	0.57	0.61	0.60	0.73	0.67
4
Absorbed dose per unit administered activity for rhTSH (mGy/MBq)	0.10	0.11	NA	NA	0.068
Absorbed dose per unit administered activity for THW (mGy/MBq)	0.11	0.10	NA	NA	0.080
THW/rhTSH ratio	1.1	0.91	NA	NA	1.2

NA = not applicable.

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TABLE 4

Calculated Tumor Absorbed Dose per Unit Administered Activity of ¹³¹I and Ratio in Tumor-Absorbed Dose (THW/rhTSH)

Tumor no.	Tumor volume (cm³)	Absorbed dose per unit administered activity (mGy/MBq) for rhTSH	Absorbed dose per unit administered activity (mGy/MBq) for THW	THW/rhTSH ratio
Patient 1
1	1.5	2.8	8.6	3.1
2	0.98	11	18	1.6
3	0.46	3.8	20	5.3
4	0.87	2.6	18	7.0
5	0.50	17	82	4.9
6	1.2	9.7	27	2.7
7	1.1	21	40	1.9
8	1.7	0.84	4.6	5.5
9	0.89	3.8	12	3.3
Patient 2
1	0.67	0.045	1.3	28
2	0.38	0.089	2.2	25
Patient 3
1	2.2	5.2	20	3.9
2	11	0.66	1.1	1.7
3	2.9	0.36	0.56	1.5
4	3.8	1.9	1.6	0.83
5	34	4.8	4.8	1.0
6	12	5.4	0.92	0.17
7	1.5	19	21	1.1
8	1.7	0.34	0.42	1.2
9	4.3	0.20	0.12	0.63
10	47	1.9	2.1	1.1
11	9.0	0.36	0.65	1.8