Nail Trace Element Profiling in Cancer Patients versus Healthy Controls: A Pilot Case-Control Study Using Energy-Dispersive X-ray Fluorescence Spectroscopy in Sebha City, Libya

Abstract

Trace element dysregulation is increasingly implicated in carcinogenesis, yet, to our knowledge, the nail metallome of Libyan cancer patients has not previously been characterized. Toenails provide a time-integrated, non-invasive biomarker of systemic metal exposure that is well suited to resource-constrained clinical settings. This pilot case–control study enrolled 16 histologically confirmed cancer patients and 7 healthy controls at Sebha Medical Oncology Centre, Libya. Concentrations of 12 elements (Cu, Zn, Se, Mn, Fe, Pb, Cd, As, Cr, Ni, Hg, Al) were measured in toenail specimens by energy-dispersive X-ray fluorescence (EDXRF) spectroscopy. Statistical comparisons used Mann–Whitney U and independent t-tests, with Bonferroni correction for multiple comparisons. Cancer patients showed significantly elevated copper (22.40 vs 12.86 µg/g; p = 0.0002) and reduced zinc (80.79 vs 127.26 µg/g; p = 0.0001) and selenium (0.55 vs 1.15 µg/g; p = 0.0001) relative to controls (all Bonferroni-corrected). Six of seven toxic metals (Pb, Cd, As, Cr, Ni, Hg) were significantly elevated after correction; exceedance of reference thresholds reached 100% for lead and 81.2% for arsenic. The Cu/Zn ratio was substantially higher in cancer patients (0.294 vs 0.101; p < 0.001; Cohen's d = 2.52), with 75% of cases exceeding the proposed threshold of 0.25. Robust inter-element antagonisms were identified between selenium and mercury (rho = −0.745) and between zinc and arsenic (rho = −0.674). This pilot study provides the first local evidence of nail trace element dyshomeostasis among Libyan cancer patients, characterized by concurrent essential element depletion and toxic metal accumulation. The Cu/Zn ratio emerges as a candidate composite biomarker. These hypothesis-generating findings support a larger, prospective, age- and sex-matched investigation.