Theranostic role of radiolabelled RGD peptide in the treatment of radioiodine-resistant thyroid cancer: A novel agent

A 47 yr old female†, a known case of papillary carcinoma thyroid, post-total thyroidectomy and radioiodine treatment (I-131, cumulative dose of 716 mCi), presented to the department of Nuclear Medicine, Postgraduate Institute of Medical Education & Research, Chandigarh, India, in June 2019, with rising serum thyroglobulin (Tg) level of 13,840 ng/ml and anti-Tg of 34.53 IU/ml. Ultrasonography of the neck revealed a lobulated heterogeneous soft tissue mass in the midline and supraclavicular region, along with bilateral subcentimetric cervical lymph nodes. There was markedly elevated serum Tg and negative whole-body radioiodine scan, also known as TENIS (Thyroglobulin Elevation with Negative Iodine Scintigraphy) syndrome (Fig. 1). The patient was evaluated with whole-body gallium-68 (Ga-68) RGD positron emission tomography/computed tomography imaging (Fig. 2) for the staging and tumour tracer avidity for therapeutic potential with radionuclide therapy. RGD is an arginine–glycine–aspartic acid-based synthetic peptide targeting integrin αvβ3, which are overexpressed on endothelial cells of neovasculature and tumour cells. Lutetium-177 (Lu-177) RGD (~120 mCi) radionuclide therapy was given to the patient in view of tracer avidity in the residual/recurrent disease, and post-therapy images showed effective localization of tracer (Fig. 3). Lu-177 RGD may be a novel approach of treatment for radioiodine refractory thyroid cancer patients. Followup of the patient after four weeks of therapy showed significant reduction in serum Tg level from 13,840 ng/ml to 5,280 ng/ml with significant clinical improvement. The patient was planned for the second dose of Lu-177 RGD radionuclide therapy in view of favourable response.

Close

Fig. 1 Whole-body (anterior and posterior) low dose radioiodine diagnostic scan done after 48 h of 2 mCi of I-131administration. No abnormal tracer uptake was seen anywhere in the body apart from physiological tracer distribution.

Export to PPT

Close

Fig. 2 (A) Whole-body Ga-68 RGD positron emission tomography(PET)/computed tomography (CT) (3.25 mCi) for residual disease and tracer avidity evaluation showed increased tracer uptake in the neck region (SUVmax 8.8) on maximum intensity projection (MIP) image. (B) Transaxial PET/CT and (C) computed tomography images showing tracer uptake in heterogeneously enhancing soft tissue lesion in the anterior of neck with tracheostomy tube in situ (arrows). (D and E) Another focal tracer uptake was seen in lytic lesion in the manubrium.

Export to PPT

Close

Fig. 3 Whole-body (anterior and posterior) post-Lu-177 RGD radionuclide therapy images at 17 h (A and B) and 48 h (C and D) showing increased tracer uptake in neck region (arrowheads) anteriorly corresponding to tracer avid soft tissue lesion seen in pre-therapy Ga-68 RGD PET/CT scan (Fig. 2). Liver, spleen and kidneys showed physiological tracer uptake.

Export to PPT