[en] Particle induced X-ray emission technique was used to obtain the serum elemental profile of healthy subjects and breast cancer patients (BCPs) undergoing chemotherapy. Concentrations of elements K, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Se, Br, Rb, and Sr were determined. The increased levels of Ca, Cr, Fe and Cu and diminished levels of Ti, Zn, and Se observed in BCPs prior to therapy, were restored to near normal levels after the fifth cycle of chemotherapy. This work elicits a unique possibility of identifying novel trace element based anti-tumour drugs for breast cancer. (author)