Analysis of Trace Elements in Human Soft Tissues from Cancerous Patients Using X Ray Fluorescence

• Autor(a) principal: Braga, Daniel de Vasconcelos Quelhas
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/141404
• topic: Cancer; Colon; Breast; μXRF; Trace Elements; Fundamental Parameters; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Cancer is one of the largest causes of death globally, causing millions of deaths each year. Its better understanding is crucial for the development and improvement of treatments. In recent years, trace elements have been used as biomarkers for carcinogenesis, but the number of studies on this subject is small due to the difficulty in obtaining a statisti- cally meaningful number of samples. The use of formalin fixed paraffin embedded (FFPE) samples, which are widely avail- able in hospitals, is a potential solution to the scarcity of samples, but their analysis is harder due to the presence of the paraffin. In this work, a total of 58 normal-tumor pairs of FFPE samples were analyzed (30 pairs of colon samples and 28 of breast samples) with the goal of developing a method capable of overcoming the difficulties imposed by the paraffin, and producing an accurate comparison between the concentration of trace elements in normal and tumor tissue. The samples were analyzed with the M4 TORNADO μXRF spectrometer. An image processing tool was developed in R to select the best areas on the sample to extract the spectra. The quantitative analyses was done with the Fundamental Parameters Method with the use of two matrices, one for colon (38% H, 11% C, 3% N and 46% O) and one for breast (39% H, 22% C, 2% N and 35% O). The matrix compositions were determined based on the mean Z of the FFPE samples for each organ, obtained through the determi- nation of the Compton-to-Rayleigh ration in the spectra and comparison with a reference curve. The statistical analysis was performed in R. The Shapiro-Wilk test was applied to test the normality of the distributions of each element in each type of tissue. To compare the normal and tumor distributions of each element, two non-parametric tests were used: the Kruskal-Wallis test and the Wilcoxon test. The elements that were found to be potential tumor biomarkers were P and S in colon, and P, S, Ca, Fe and Zn in breast. In colon, significant changes were also found in Fe and Ni, but more research is needed to conclude about their involvement in carcinogenesis.