Reply: Different Radionuclides in DOTA-EB-TATE Effect Different Uptake in Somatostatin Receptor–Positive HEK293 Cells

REPLY: We would like to thank Dr. Kotzerke and his colleagues for the important insights into the uptake of DOTA-EB-TATE, an albumin-binding octreotate developed by us (1–4). The results presented by Dr. Kotzerke are of high importance, suggesting that the radiometal chelated into the DOTA moiety affects the uptake and perhaps binding of both DOTA-TATE and EB-DOTA-TATE. The authors concluded that “As a consequence of the different uptake, only different isotopes of the same element (such as ⁸⁶Y/⁹⁰Y or ⁶⁴Cu/⁶⁷Cu) can be used for assessment of biokinetic data.”

Although the data presented by the authors are intriguing, we would like to argue that: (1) These results are not specific to EB-DOTA-TATE but are seen with DOTA-TATE as well. It is common practice to use ⁶⁸Ga-DOTA-TATE to detect tumor somatostatin receptor 2 expression before radionuclide therapy with ¹⁷⁷Lu-DOTA-TATE, and so far this practice seems to prove itself. Moreover, ⁶⁸Ga-DOTA-TATE scanning has significantly lower radiation exposure to the patient than other longer-lived isotopes labeled with the same ligand. It would be unreasonable in our opinion to use ⁸⁶Y for imaging when a much safer option is available (2). The authors derive their conclusion from in vitro cell uptake and extrapolated the result to predict the in vivo pharmacokinetics. It would be more appropriate to draw a conclusion from actual in vivo studies.

We look forward to seeing data from more in-depth in vivo studies done, perhaps, by Dr. Kotzerke and colleagues.

• © 2019 by the Society of Nuclear Medicine and Molecular Imaging.