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Simultaneous Quantification of Aromatase Inhibitors and Estrogens in Postmenopausal Breast Cancer Patients
Bjørn-Erik Bertelsen1, Kristin Viste1, Thomas Helland1
1Hormone Laboratory, Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Vestland, 5009, Norway.
Context:
Currently there are no assays that can simultaneously quantify serum levels of the third-generation aromatase inhibitors (AIs): letrozole, anastrozole, and exemestane, and the ultra-low levels of estrogens in postmenopausal breast cancer patients on AI treatment. Such measurements may be pivotal for the determination of optimal and individualized treatment regimens. We aimed at developing a liquid chromatography-tandem mass spectrometry (MS/MS) method for simultaneous assessment of letrozole, anastrozole, exemestane, and 17-hydroxyexemestane as well as subpicomolar levels of estradiol and estrone.
Methods:
Internal standards, calibrators, serum samples, and quality controls were in fully automated steps transferred to a deep-well plate for a 2-step liquid-liquid extraction. The extracts were reconstituted and analytes were separated chromatographically using 2 serially coupled columns, then subject to MS/MS in electrospray ionization mode. The method was thoroughly validated and is traceable to 2 accredited estrogen methods.
Results:
The measurement range for estrone and estradiol was 0.2 to 12 000 pmol/L and 0.8 to 13 000 pmol/L, and covered the expected therapeutic range for the AIs. All analytes had a precision of less than or equal to 13%, and accuracies within 100 ± 8%. As proof of concept, AI and estrogen levels were determined in serum samples from postmenopausal breast cancer patients under treatment.
Conclusion:
We present here an assay suitable for the simultaneous measurement of serum levels of all third-generation AIs and ultra-low levels of estrogens, providing a powerful new tool to study drug efficacy and compliance. The method is highly valuable for postmenopausal patients whose pretreatment estradiol levels are below the threshold of detection for most routine assays, but still require suppression.
Insights
A new assay accurately measures third-generation aromatase inhibitors (AIs) and ultra-low estrogen levels in breast cancer patients. This breakthrough aids in optimizing individualized AI treatment and monitoring drug efficacy and compliance.
Area of Science:
- Endocrinology
- Pharmacology
- Analytical Chemistry
Background:
- Current assays cannot simultaneously measure third-generation aromatase inhibitors (AIs) and ultra-low estrogen levels in postmenopausal breast cancer patients.
- Accurate quantification is crucial for optimizing individualized AI treatment regimens.
Purpose of the Study:
- To develop a liquid chromatography-tandem mass spectrometry (MS/MS) method for simultaneous quantification of letrozole, anastrozole, exemestane, and their metabolites, alongside subpicomolar levels of estradiol and estrone.
- To provide a tool for assessing drug efficacy and patient compliance in breast cancer treatment.
Main Methods:
- A fully automated, two-step liquid-liquid extraction process was employed.
- Analytes were separated using serially coupled columns and detected by MS/MS in electrospray ionization mode.
- The method was validated and is traceable to accredited estrogen assays.
Main Results:
- The assay measures estrone (0.2–12,000 pmol/L) and estradiol (0.8–13,000 pmol/L), covering therapeutic ranges.
- All analytes demonstrated high precision (≤13%) and accuracy (within 100 ± 8%).
- The method was successfully applied to measure AI and estrogen levels in patient serum samples.
Conclusions:
- A novel assay enables simultaneous measurement of third-generation AIs and ultra-low estrogen levels.
- This method serves as a powerful tool for studying drug efficacy and compliance in postmenopausal breast cancer patients.
- It is particularly valuable for patients with pre-treatment estradiol levels below standard assay detection limits.
