90Y-DOTATOC therapy in patients with metastatic radioiodine negative differentiated thyroid cancer: Preliminary results

Objectives Metastases (mts) from differentiated thyroid carcinoma (DTC) can lose in time the capacity to concentrate radioiodine and the possibility to have a specific treatment. DTC may express somatostatin receptors; this offers a new opportunity of treatment. Aim of the study is to evaluate the utility of somatostatin analog DOTA-D-Phe1 -Tyr3-octreotide (DOTATOC), radiolabelled with 90Y for therapy, in these pts.

Methods 28 pts (m/f 13/15; age 22-81 yrs, mean 59) with non-radioiodine-avid DTC, metastatic or suspicious metastatic underwent 68Ga-DOTATOC PET/CT. Fourteen pts had positive PET. Eight of these with high uptake mts had 90Y- DOTATOC therapy. The total dose (5-15 GBq in 2-6 cycles) was calculated according to clinical status and dosimetry evaluation by 111In-DOTATOC scintigraphy. The monitoring of treatment was made by clinical and laboratory findings and PET/CT (functional volume, SUV, tumor/muscle SUV).

Results In this study we evaluates the 7 pts who have already completed the treatment and have at least a 6 month follow up. Three pts had a partial response (PR), 2 are in stable disease (SD) and 2 in progression (P). Evaluating the mts site we had 2 PR, 2 S and 2 P in bone mts; 2 RP, 2 RC and 2 P in lymph node mts; 1 S, 1 PR and 1 complete response in lung mts. The correlation tireoglobulin value/other findings is in progress. The clinical response is superior to the PET/CT findings. The pts had only minimal side effects as fatigue and nausea.

Conclusions Labelled somatostatin analogs are very interesting for pts with progressive radioiodine-negative DTC. The possibility to use the same peptide for therapy in PET positive pts is promising but needs further confirmation in larger number of pts