In the beginning, nuclear medicine was radionuclide therapy, which has evolved into molecular tumour-targeted control of metastatic cancer. Safe, efficacious, clinical practice of therapeutic nuclear oncology may now be based upon accurate personalised dosimetry by quantitative gamma SPECT/CT imaging to prescribe tumoricidal activities without critical organ toxicity. Preferred therapy radionuclides possess gamma emission of modest energy and abundance to enable quantitative SPECT/CT imaging for calculation of the beta therapy dosimetry, without radiation exposure risk to hospital personnel, carers, family or members of the public. The safety of outpatient radiopharmaceutical therapy of cancer with Iodine-131, Samarium-153, Holmium-166, Rhenium-186, Rhenium-188, Lutetium-177 and Indium-111 is reviewed. Measured activity release rates and radiation exposure to carers and the public are all within recommendations and guidelines of international regulatory agencies and, when permitted by local regulatory authorities allow cost-effective, safe, outpatient radionuclide therapy of cancer without isolation in hospital.