[18F]TFB PET/CT May Predict [18F]TFB/FDG Positivity in Differentiated Thyroid Cancer

"[18F]TFB PET might offer a noninferior diagnostic performance compared with [131I]iodine imaging with therapeutic activities," according to the study authors.

Use of [18F]TFB PET/CT prior to treatment with radioactive [131I]iodine therapy (RAI) may be predictive of recurrent differentiated thyroid cancer (DTC) tumors, according to data from a retrospective study published in The Journal of Nuclear Medicine.

Investigators identified a total of 62 lesions via [18F]TFB PET/CT, 32 of which (52%) were [18F]TFB positive and 52 (84%) were [18F]FDG positive. Of the 30 lesions that were identified as being [131I]iodine-positive (48%), investigators reported that 3 were false positive iodide uptakes.

“Despite multiple imaging options, accurate diagnosis of recurrent DTC remains challenging,” lead study author David Ventura, MD, of the Department of Nuclear Medicine, University Hospital Muenster, in Muenster, Germany, and coinvestigators wrote in the publication. “Appropriate therapeutic decisions are especially difficult to make in cases of incipient dedifferentiation or [thyroglobulin elevated and negative scintigraphy] TENIS syndrome. Here, 26 patients who received [18F]TFB PET/CT and [131I]iodine TxWBS-SPECT/CT have been analyzed. The detection rate of both tracers was relatively similar, but slightly more lesions could be identified positive on [18F]TFB PET/CT. This indicates that [18F]TFB PET/CT might help in the selection of DTC patients for RAI.”

The single-center, retrospective study included 26 patients who had been diagnosed with recurrent disease that was treated with high-activity RAI that ranged between 5.00 to 10.23 GBq. Patients were treated from May 2020 to November 2022. Every patient received [18F]TFB PET/CT prior to RAI due to its higher diagnostic accuracy. This was done in routine clinical practice to assess the potential of localized treatment strategies.

A local tumor board recommended high-activity RAI based on international guidelines. Additionally, all patients included in the study underwent TxWBS-SPECT/CT following RAI, and [18F]FDG PET/CT was used in individuals with evidence of dedifferentiation. More than half of patients were male (53.8%) and 50.0% had follicular thyroid carcinoma histology. The median patient age was 64.5 years (range, 38-87).

The study population received 2 thyrotropin alfa (Thyrogen) intramuscular injections of 0.9 mg at 24 and 48 hours prior to treatment. Oral [131I]iodide was administered at a median activity of 6.02 GBq (range, 5.00-10.23) following PET acquisition.

Patients underwent [18F]FDG PET/CT if there was suspicion of dedifferentiated cancer, and eligible patents were imaged following 6 hours of fasting. All images were then reviewed by 2 nuclear medicine physicians.

The 26 individuals underwent [18F]TFB PET/CT, RAI and [131I]iodine TxWBS-SPECT/CT, and met the inclusion criteria for the retrospective study. Investigators reported that high-activity RAI provided imaging evidence of both lymph node and distant metastases on [18F]FDG PET/CT (84.6%), ultrasound (7.7%), MRI (3.9%), and [131I]iodine diagnostic whole-body scintigraphy (WBS; 3.9%).

Local recurrence was reported in 13.6%, lymph node metastases in 22.7%, lung metastases in 30.9%, bone metastases in 36.3%, and metastases in other organs in 9.1% of patients with available [18F]FDG PET/CT. Additionally, the median time from [18F]TFB PET/CT/RAI to [131I]iodine TxWBS-SPECT/CT was 3.8 days (95% CI, 3.3-4.2). Ninety-six percent of patients received [18F]FDG PET/CT under suspicion of dedifferentiated disease. Additionally, the time between [18F]TFB PET/CT/RAI to [18F]FDG PET/CT was 32.8 days (95% CI, 18.3-47.3).

“[18F]TFB PET might offer a noninferior diagnostic performance compared with [131I]iodine imaging with therapeutic activities,” the investigators concluded. “Together with [18F]FDG PET, [18F]TFB PET might establish a new quantitative measure of differentiation/dedifferentiation for optimal therapeutic management of recurrent DTC with suspicion of dedifferentiation. Further prospective studies on the clinical implementation of [18F]TFB are warranted.”

Reference

Ventura D, Dittmann M, Büther F, et al. Diagnostic performance of [18F]TFB PET/CT compared with therapeutic activity [131I]iodine SPECT/CT and [18F]FDG PET/CT in recurrent differentiated thyroid carcinoma. J Nuc Med. 2024;65(1). doi:10.2967/jnumed.123.266513