Value of Tl-201 imaging in predicting therapeutic I-131 uptake in patients with thyroglobulin-positive but I-131 scan negative differentiated thyroid cancer
The Philippine Journal of Nuclear Medicine
;
: 8-13, 2016.
Article
in English
| WPRIM
| ID: wpr-633549
ABSTRACT
BACKGROUND:
Serum thyroglobulin assays and I-131 imaging and routinely employed for the detection of remaining functioning thyroid tissue after surgery and radioiodine therapy. However, the sensitivity of I-131 is suboptimal resulting in cases of positive thyroglobulin test but negative I-131 imaging, potentially creating a dilemma in subsequent therapeutic management. Other radiopharmaceuticals, such as TI-201 may offer better sensitivity, although it is not clear whether this contributes to the decision-making for subsequent I-131therapy. This prospective cohort study aimed to determine if Tl-201 imaging identified thyroid tissues that will take up therapeutic I-131, and to help define its clinical utility.METHODS:
Fourteen consecutive patients who underwent surgery for well-differentiated thyroid cancer, had I-131 therapy at least eight months previously, and with elevated thyroglobulin (>10 ng/mL) but negative pre-therapy (111 MBq) I-131 whole body scan (WBS), were enrolled in the study. WBS was done using 56.74 MBq of Tl-201. All patients had repeat I-131 ablation (3.7-7.4GBq) one to two months after Tl-201 imaging. Post-therapy WBS was done four to seven days after.RESULTS:
All 14 patients had papillary thyroid carcinoma. Ten patients had a positive Tl-201 scan. Of the 14 subjects, only two had a positive post-therapy I-131 WBS, both whom had a positive Tl-201 scan. Thallium-201 scanning showed a fairly high sensitivity (71%) in demonstrating thyroid remnants or metastases using a thyroglobulin level of >10 ng/mL as standard. However, a positivel Tl-201 scan only has a predictive value of 20% for subsequent uptake of therapeutic I-131 as shown in the post-therapy scan.CONCLUSION:
Thallium-201 uptake correlates poorly with therapeutic I-131 uptake in thyroglobulin-positive, but I-131 scan-negative, differentiated thyroid cancer patients. Results of this study suggest that the presence of thyroid remnants and metastases on Tl-201 imaging is inappropriate as a basis for subsequent I-131 therapy.
Full text:
Available
Index:
WPRIM (Western Pacific)
Main subject:
Thallium
/
Thyroglobulin
/
Thyroid Neoplasms
/
Thallium Radioisotopes
/
Carcinoma
/
Neoplasms, Second Primary
/
Radiopharmaceuticals
/
Thyroid Cancer, Papillary
/
Iodine Radioisotopes
Type of study:
Observational study
/
Prognostic study
Limits:
Adult
/
Female
/
Humans
/
Male
Language:
English
Journal:
The Philippine Journal of Nuclear Medicine
Year:
2016
Type:
Article
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