Lung uptake on I-131 therapy and short-term outcome in patients with lung metastasis from differentiated thyroid cancer

Abstract

Objective: It is sometimes difficult to assess I-131 lung uptake at the initial I-131 therapy because of strong artifacts from I-131 uptake in the thyroid bed. The aim of this study was to analyze the lung uptake at the second I-131 therapy for lung metastasis in patients who did not have lung uptake at the initial therapy from differentiated thyroid carcinoma (DTC). Then, we also analyzed the relationship between the initial lung uptake and short-term outcome after I-131 therapies.

Methods: This study included 62 DTC patients with lung metastasis. The patients were classified into 2 groups according to the lung uptake at the initial I-131 therapy such as patients with lung uptake (positive uptake group n = 31) and those without lung uptake (negative uptake group n = 31). The lung uptake was analyzed at the second therapy in both groups. The short-term outcome was also analyzed based on the CT findings of lung metastasis size and serum thyroglobulin level between the two groups.

Results: The positive uptake group showed positive lung uptake at the second therapy in 23 patients (74 %), whereas none of negative uptake group showed any lung uptake at the second therapy (P < 0.01). The positive uptake group significantly decreased in the size of lung metastasis from the initial therapy to the second therapy (20.0 ± 11.7 to 16.6 ± 9.6 mm, P < 0.01) with further decrease after the second therapy (P < 0.05). The serum thyroglobulin level was also significantly decreased from the initial therapy to the second therapy (4348 ± 7011 to 2931 ± 4484 ng/ml, P < 0.05). In contrast, the negative uptake group significantly increased in the size of lung metastasis from the initial therapy to the second therapy (17.3 ± 12.2 to 19.9 ± 14.3 mm, P < 0.01) with further increase after the second therapy (P < 0.01).

Conclusion: No patients without lung uptake at the initial I-131 therapy showed lung uptake at the second therapy, or showed treatment effect. Therefore, second I-131 therapy for these patients with initially negative lung uptake should be considered cautiously.

Fig. 1

Flow chart of lung uptake of ¹³¹I at the initial therapy and at the second therapy

Fig. 2

The sum of lung metastatic nodule. a In the positive uptake group, lung metastases became significantly smaller after the initial and the second therapy by Wilcoxon Matched-Pair Signed-Rank Test. b Metastatic lung nodules became significantly enlarged after the initial and the second therapy in the negative uptake group

Fig. 3

a A 45-year-old female with lung metastases from papillary carcinoma of the thyroid. (a) CT image at the initial therapy shows multiple lung metastases. (b) In the initial therapy, a post-therapeutic ¹³¹I scan suggested high uptake both in the thyroid bed and lower lung. (c) CT at the second therapy demonstrated that lung metastasis had got smaller. (d) In the second therapy, ¹³¹I scan showed also high uptake in lower lung. (e) Thirteen months after the second therapy, the lung nodule was further reduced on CT. Thyroglobulin at the initial therapy was 2768 ng/ml, and that at the second therapy had fallen to 2383 ng/ml. b A 53-year-old female with lung metastases from papillary carcinoma of the thyroid. (a) CT image at the initial therapy demonstrates multiple lung metastases. (b) Post-therapeutic ¹³¹I scan at the initial therapy showed high uptake in the thyroid bed but no uptake in the lung. Physiological uptake in intestinum is shown. (c) The metastatic nodule had grown larger on the CT at the second therapy. (d) At the second therapy, the ¹³¹I scan showed uptake in intestinum and salivary glands physiologically, but no lung uptake even though the thyroid bed uptake had disappeared. (e) CT image 21 months after the second therapy. Lung metastases had progressed in size. Serum thyroglobulin was increased from 844 ng/ml at the initial therapy to 2352 ng/ml at the second therapy

Fig. 4

Thyroglobulin level at the ¹³¹I therapy. a In the positive uptake group, thyroglobulin at the second therapy significantly decreased from that at the initial therapy by Wilcoxon Matched-Pair Signed-Rank Test. b Thyroglobulin at the second therapy tended to increase from that at the initial therapy in the negative uptake group