Summary and Aims. Radionuclide therapy is one of the accepted cancer treatment modalities available nowadays. Different to conventional chemotherapy, the main mechanism action of any radionuclide therapy in cell killing is primarily by inducing damage following exposure to highly destructive ionising radiation (α and β particles). Targeting with radionuclide therapy can be provided by conjugating radionuclides to targeting molecules. Radionuclide therapy in general can be utilised in different situations due to different characteristics. α particles for instance produce highest LET, travelling distance to up to 100 µm making them suitable for solid large cancers lesions although administration in high amount might be an issue due to toxicity to critical organs. β particles produced much lower LET due to extended distance travelled making them suitable for targeting large solid tumours. Like α particles, therapy with β particles exposes patients to non-specific toxicity to critical organs. Auger electrons on the other hand have high LET and travel short distances creating a need for localisation within the target cells for any damage to occur. Therefore, it is postulated that Auger electron therapy is best utilised against small metastatic lesions or single circulating tumour cells. Auger emitters damage cells based on two mechanisms: 1) via production of highly ionising Auger electrons and 2) coulombic explosion of the atom core following release of electrons. As Auger emitters have different profiles in Auger electrons productions, it is possible to select emitters that produced most numbers and energetic Auger electrons for therapeutic purposes. 67Ga has potential as it produces comparatively energetic Auger electrons able to travel further than Auger electrons from many other radionuclides. Therefore, there is higher chance they can reach and disrupt critical cellular components. In vivo and in vitro studies showed that 67Ga produced high cell killing with high specificity. However, due to lack of understanding of its radiochemistry and efficient chelators, it was later neglected. Current interest in 68Ga has led to better understanding of gallium chemistry. The knowledge can be transferred to 67Ga making re-evaluation of 67Ga for therapeutic purposes possible and timely.
