The present invention relates to the generation of an Atomic Therapeutic Indicator (ATI) for a test sample by the quantification of manganese in voxels of a 3D region of the sample wherein the 3D region is topographically defined by co ordinates XxYxZ. The ATI is used to assess the radio responsiveness i.e. sensitivity or resistance to radiation treatment of a cancer i.e. a tumour/neoplasm. In a preferred embodiment the present invention relates to a method of generating the ATI assessing the radio responsiveness of a tumour/neoplasm based on the ATI and based on the assessment either treating or not treating the tumour with radiation. The present invention also relates to a method of determining if a cancer is likely to reoccur post radiation treatment comprising quantifying the level of manganese in voxels of a 3D region of a test sample from the cancer and determining the frequency of high metallomic regions (HMRs) in the cancer wherein a high frequency of HMRs is indicative that the cancer is likely to reoccur and a low frequency of HMRs is indicative that the cancer is unlikely to reoccur and associated methods of treatment.
