Utility of non-contrast Dual Energy Computed Tomography in diagnosis of differentiated thyroid cancer – two case study

Patient Two, a 74-year-old female, was admitted to the hospital for treatment of pT1(m)N0 follicular thyroid carcinoma (FTC). She underwent thyroidectomy with central lymphadenectomy and was referred to the hospital for RAI therapy. During neck USG no sign of residual disease was found. In the day of admission Tg levels was > 500ng/ml [N: 3.5–77] and aTg was 136 IU/ml [N: 0-115 IU/ml]. After rhTSH administration (0,9 mg for two consecutive days) Tg was 28387ng/ml. She received 120mCi of 131I. Moreover 18 F-FDG PET was performed. Examination showed metabolically active lymph nodes: subaortic 8 × 6 mm (Standard Uptake Value [SUV] − 4,4), and paratracheal left 8 × 6 mm (SUV − 2,4). There was also morphological presence of multiply pulmonary nodules (up to 12 mm) but with no excessive metabolism of 18 F-FDG. Next, the DECT was performed, and showed high iodine concentration in previously observed lung nodules – giving suspicion of FTC metastasis (Fig. 5). In control 2 months after RAI we noticed output Tg concentration of 24832.00 ng/ml [N: 3.5–77], slightly increased aTg 121 IU/ml [N: 0–115], and stimulated Tg 30767.00 ng/ml [N: 3.5–77]. Patient underwent additional course of RAI therapy (200mCi). Post therapeutic scintigraphy showed no sign of radioiodine accumulation. Suspicious lymph nodes described in PET was biopsied, with a result of pneumoconiosis lymphadenopathy (Fig. 6). Due to divergent results of DECT, biochemical tests, PET, and scintigraphy the decision was made to perform histopathological biopsy of lung. Fragment of the lung with suspicious nodules (typed by DECT) was harvested. Pathological report showed located in the lung parenchyma cancer metastasis with an immunohistochemical profile corresponding to the primary focus in the thyroid gland: Tg(+), TTF-1(+), CDX2 (-), S100(-), EMA(-), ER(-) (Figs. 7, 8 and 9). Patient was qualified to sorafenibe therapy. After 4 weeks of sorafenibe − 200 mg two times a day (BID) - Tg levels decreased to 2020 ng/ml, and aTg titre decreased to 12 IU/ml (both results decreased over 10x). Further increase of sorafenibe daily dose to 400 mg BID decreased Tg even to 1314 ng/ml. Present dose was tolerable, and patient stayed under control of our clinic, with no serious adverse events observed, and stabilization of cancer progression.

Fig. 5figure 5

DECT analysis of thyroid cancer metastases to the lung. Solid lung tumor in the left lower lobe of the left lung (L1 - blue). Tumor densities − 3,67 ± 10.82 HU measured on invert gray maps improving visibility of the lesion A. High index of endogenous iodine accumulation 12.33 ± 2.10 × 100 µg / cm3 suggest metastasis of thyroid cancer B. Analysis of another nodule (L2 - red) also in the lower lobe of the left lung (C, D). Tumor density + 7.85 ± 8.49 HU C. Lower index of endogenous iodine accumulation 4.65 ± 3.28 × 100 µg / cm3 D. Comparison of X-ray absorption analysis by L1 and L2 in graphs showing ionizing radiation absorption curves as a function of photon energy in the range of 40–140 keV in the range of 5 keV (E)

Graphical representation of the distribution of iodine accumulation in L-1 and L-2 in the form of percentage distributions of pixels, one of the examples of the metastases F. The tumor L1 – blue showed a greater accumulation of endogenous iodine compared to the tumor at the site of L2 – red.

Fig. 6figure 6

Pneumoconiosis lymphadenopathy. HE staining, magnification – 57x. Black spots represents accumulation of carbon dust deposits

Fig. 7figure 7

Lung nodule harvested due to DECT locating. HE staining, magnification – 1,72x and 38x

Fig. 8figure 8

Lung nodule harvested due to DECT locating. Thyroglobulin staining, magnification – 4.63x

Fig. 9figure 9

Lung nodule harvested due to DECT locating. TTF1 staining, magnification − 14.6x

Commentary and future use of the method

Both cases showed value of DECT in diagnosis of differentiated thyroid cancer. Especially in borderline cases, like in case 2 presented in the text, the method could help to locate DTC metastasis allowing to quick introduce proper treatment.

No use of iodine contrast agent, which can postpone RAI therapy or cause allergic reactions, was the biggest advantage. However, the American Thyroid Association (ATA) guidelines claims that exogenous iodine, like iodine contrast factor, is generally cleared within 4–8 weeks after administration in most patients, and does not postpone RAI treatment [20]. The European Guidelines due to different iodine supply speaks for extending this period to at least 6–12 weeks (the best for 20 weeks), to ensure total iodine clearance [21]. It is also worth noticing that ATA guidelines are based on the study, which was conducted on relatively low (25) number of patients, and included assessment of urine iodine [22]. We have also to remember about potential saturation and accumulation of cells with iodine, which can reduce effectiveness of RAI treatment.

There are no doubts, that primary techniques for diagnosis of DTC metastases are USG and FNAC [20, 21]. However, the guidelines underline the role of contrast-CT as primary examination in locating distant DTC metastases. On the other hand, every CT is increasing radiation of the patient, and iodine contrast can cause allergic reactions, kidney injury or delay of RAI treatment [20].

That is why, we consider non-contrast DECT as an important additional diagnostic tool in patients after thyroidectomy, with biochemical signs of possible metastatic or recurrent disease where neither ultrasound nor RAI scintigraphy, nor 18 F-FDG PET shows localization of DTC metastases. Also patients with contraindications for iodine contrast administration (allergy, kidney disease) can benefit from this kind of examination. Presented cases confirmed that DECT was able to locate cancer metastases, indicate them to surgeon, and after histological confirmation, to introduce suitable therapy.

留言 (0)

沒有登入
gif