Preparation of Patient Doses of 177 Lu-DOTA-TATE Using Indigenously Produced 177 Lu: The Indian Experience

Abstract

Purpose:

¹⁷⁷Lu (T _1/2 = 6.73 days, E _β(max) = 0.497 MeV, E _γ = 113 KeV [6.4%] and 208 KeV [11%])-labeled DOTA-TATE, a somatostatin analog, is presently being considered a promising agent for the treatment of patients suffering from inoperable neuroendocrine tumors, which overexpress somatostatin receptors. The objective of the present work was to develop an optimized protocol for the preparation of therapeutic dose of ¹⁷⁷Lu-DOTA-TATE with as high as achievable specific activity at the time of its administration, taking into account the variable specific activity of ¹⁷⁷Lu available during the preparation of the agent.

Methods:

¹⁷⁷Lu labeling of DOTA-TATE was carried out using a precalculated amount of DOTA-TATE based on the available specific activity of ¹⁷⁷Lu at the time of preparation, keeping a minimum molar ratio of [DOTA-TATE]:[Lu] = 4:1, so that ¹⁷⁷Lu-DOTA-TATE could be obtained with highest possible specific activity without compromising its radiochemical purity and stability.

Results:

One hundred (100) batches of ¹⁷⁷Lu-DOTA-TATE were prepared following this protocol till date at five different nuclear medicine centers of India, with a radiochemical purity of 98.25% ± 1.1% and specific activity of 32.74–65.49 GBq/μmol (885–1770 mCi/μmol). Till date, 250 patient doses of ¹⁷⁷Lu-DOTA-TATE have been dispensed and administered in 150 patients suffering from various types of neuroendocrine-originated tumors.

Conclusions:

The developed method ensures that patient doses of ¹⁷⁷Lu-DOTA-TATE could be prepared with highest possible specific activity depending upon the available specific activity of ¹⁷⁷Lu at the hospital radiopharmacy.