Preliminary results using a kit to measure tamoxifen and metabolites concentrations in capillary blood samples from women with breast cancer

Abstract

The aim of the study was to compare 3 blood sampling methods, including capillary blood sampling, for determining Tamoxifen (TAM), Z-endoxifen (END), and 4-hydroxytamoxifen (4HT) concentrations. High performance liquid chromatography-mass spectrometry was used to quantify concentrations of TAM, END, and 4HT in plasma, venous blood, and capillary blood samples of 16 participants on TAM therapy for breast cancer. The rhelise kit was used for capillary sampling. Calibration curves using 13C-labeled analogs of TAM, END, and 4HT as internal standards were used for quantifications. A capillary sampling kit was used successfully for all participants. Mean TAM concentrations did not differ significantly in the 3 types of samples. Mean END and 4HT concentrations did differ significantly between capillary and venous blood samples, possibly related to photodegradation in the internal standards prior to use or degradation products with chromatographic retention times similar to the metabolites. TAM, END, and 4HT concentrations were relatively stable when stored for 14 days at 8 °C and 20 °C. Therapeutic drug monitoring of TAM using an innovative kit and capillary blood sampling is feasible. Preliminary data from this study will aid in developing a multicenter, randomized clinical trial of personalized TAM dose monitoring and adjustments, with the goal of enhancing the quality-of-life and outcomes of patients with breast cancer. Clinical Trial Identification: EudraCT No 2017-000641-44.

A Short Post-Reattachment Ultrasensitive Window of Time in Human Cancer Cells as Therapeutic Target of Prolonged Low-Dose Administration of Specific Compounds

“…The clinical efficacy of tamoxifen after surgery and radiation to reduce the risk of invasive breast cancer supports this conclusion [ 15 , 16 ]. In women with breast cancer, the mean concentrations of tamoxifen in plasma and venous blood were 89.31 ng/mL and 98.31 ng/mL, respectively [ 17 ]. After 28 days of treatment with a dose of 20 mg/day, the serum concentration was 83.6 (8.7–134.4) ng/mL [ 18 ].…”

“…These specific drugs can be exploited in the clinic to decrease the incidence of metastasis in specific cancers. The clinical efficacy of tamoxifen after surgery and radiation to reduce the risk of invasive breast cancer supports this conclusion [15,16]. In women with breast cancer, the mean concentrations of tamoxifen in plasma and venous blood were 89.31 ng/mL and 98.31 ng/mL, respectively [17].…”