Preparation of patient doses of (177)Lu-DOTA-TATE using indigenously produced (177)Lu: the Indian experience

(177)Lu (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 (177)Lu-DOTA-TATE with as high as achievable specific activity at the time of its administration, taking into account the variable specific activity of (177)Lu available during the preparation of the agent.

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

One hundred (100) batches of (177)Lu-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 (177)Lu-DOTA-TATE have been dispensed and administered in 150 patients suffering from various types of neuroendocrine-originated tumors.

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