Aspects of yield and specific activity of produced [sup.177]Lu used in targeted radionuclide therapy

[sup.177]Lu-labeled receptor avid peptides and monoclonal antibodies have been effectively used in targeted tumor therapy, owing to the ideally suited decay properties and favourable production logistics of [sup.177]Lu [[T.sub.1/2] = 6.65 days; [E.sub.β(max)] = 497 keV (78.6%); [E.sub.γ] = 208 keV (11.0%)]. The specific activity of [sup.177]Lu produced by the (n,γ) route is one of the important criteria, which determines the efficacy of [sup.177]Lu-labeled receptor-avid biomolecules. The present article highlights that the specific activity of (n,γ)produced [sup.177]Lu cannot be calculated by simply dividing the produced activity by the mass of the target irradiated, unlike other (n,γ)produced medical radioisotopes and there is a significant enhancement of specific activity due to the burn up of the Lu target during irradiation, which is an added advantage towards the utilization of [sup.177]Lu in receptor specific therapeutic radiopharmaceuticals. Keywords [sup.177]Lu * Targeted tumor therapy * Specific activity * Target burn-up