Proabably limited exposure can cure the cancer and excess will leads to carcinogenic.  This kind of phenomina also expected in Fluride consumption.  Lesser than 1 ppm cause beneficial effect and higher to 1.5 ppm cause ill effect on human being.

Cancer therapy by irradiation aims only at destroying tumor cells by induced defects of DNA molecules, which can not be repaired. And as John already has mentioned, this therapy only can be applied if the surrounding normal tissue survives by lower doses or by a little better resistance.

So radiation doesn´t cure cancer cells, it kills them!

Small doses of radiation don´t cure anything, they cause the development of cancer by changig the DNA sequences. So these cells raise their proliferation rate, infiltrate normal surrounding tissues and emit metastatic cells. The propabilty for this effect is proportional to the dose delivered, not the malignance of the induced tumor.

I´ve no information to the amines, because I´m not specialized to this field.

I am in agreement with Hanno & John ... Even though the ability to target only the cancerous tumor and minimize radiation exposure to healthy, surrounding tissue, has improved significantly within recent years, the phenomenon of scattering cannot be effectively controlled. As a consequence of this double-edged sword, the surrounding tissue will receive a radiation exposure and depending on the total absorbed dose, can initiate abnormalities to the DNA sequence whereby a condition for cell metastasis may evolve, creating the potential for new cancer growth.