A key advantage of<unk>  over other methods of radiotherapy is the ability to target delivery of therapeutic radionuclides directly to the tumour or target site. This works because some tumours have an abundance (overexpression) of<unk><unk> s, compared to normal tissue. A radioactive substance can be combined with a relevant<unk>  (or its analogue) so that it preferentially binds to the tumour. With a gamma emitter as the radionuclide, the technique can be used for imaging with a gamma camera or PET scanner to locate tumours. When paired with alpha or beta emitters, therapy can be achieved, as in<unk> . The current generation of<unk>  targets somatostatin<unk> s, with a range of analogue materials such as octreotide and other DOTA compounds. These are combined with indium-111, lutetium-177 or yttrium-90 for treatment. 111In is primarily used for imaging alone, however in addition to its gamma emission there are also auger electrons emitted, which can have a therapeutic effect in high doses. 90Y is bound with DOTATOC for<unk>  treatments. The natural somatostatin<unk>  ligand, the 14 amino acid<unk>  somatostatin (A), was abridged to the biologically more stable 8 amino acid<unk>  Octreotide (OC, B). Introduction of a tyrosine into the 3rd position of the Octreotide sequence resulted in Tyr3-Octreotide (TOC, C), which allows for iodination of the tyrosine residue with the γ-emitter 123I and subsequent somatostatin<unk>  targeted imaging. For the use in<unk>  TOC was coupled with the chelator DOTA, to form the octapeptide DOTA-TOC (D).<unk>  radiopharmaceuticals are constructed with three components; the radionuclide, chelator, and somatostatin analogue<unk> . The radionuclide delivers the actual therapeutic effect (or emission, such as photons, for imaging). The chelator is the essential link between the radionuclide and<unk> . For 177Lu and 90Y this is typically DOTA (tetracarboxylic acid, and its variants) and DTPA (pentetic acid) for 111In. Other chelators known as NOTA (triazacyclononane triacetic acid) and HYNIC (hydrazinonicotinamide) have also been experimented with, albeit more for imaging applications. The somatostatin analogue affects biodistribution of the radionuclide, and therefore how effectively any treatment effect can be targeted. Changes affect which somatostatin<unk>  is most strongly targeted. For example, DOTA-lanreotide (DOTALAN) has a lower affinity for<unk>  2 and a higher affinity for<unk>  5 compared to DOTA-octreotide (DOTATOC).
Peptide receptor radionuclide therapy
Radionuclide therapy
Targeted therapy
Monoclonal antibody therapy
Fluoride therapy
Multisystemic therapy
Chemoimmunotherapy
Targeted alpha-particle therapy