Methodological study using XAS of an arsenic-based antileukemia treatment

Acute promyelocytic leukemias relapses are treated by solubilised arsenic trioxide. The elimination rate of arsenic during the treatment is crucial. One way of elimination is by incorporating arsenic metabolites in hair. Micro-XANES experiments were performed at the ESRF ID-22 beamline on transversal hair cuts from two patients. A special code (LASE) was developed in order to refine the analysis of such data and led us to conclude that arsenic oxidation degree was +III. Micro-XANES experiments were coupled with x-ray fluorescence elemental maps of hair sections. Given the dilution of the samples, maps were collected on thick slices. Hence width effects became sensible and caused distortions of the final image. In order to refine the location of arsenic in hair, we developed models to handle these width effects. These models allowed us to conclude that arsenic was distributed at the periphery of hair. Statistical tests were developed to evaluate the relevance of the models.