Other safety alerts
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| Canada: FASLODEX (fulvestrant) - risk of unnecessary therapy modification due to falsely elevated estradiol levels |
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Health Canada advised that medical and scientific literature as well as post marketing reports suggest that fulvestrant can cross react with estradiol (E2) immunoassays due to structural similarity with estradiol. The false E2 positive assays may lead to misinterpretation of the menopausal status of women therefore putting patients at risk for unnecessary surgery or endocrine therapy modification.
FASLODEX® (fulvestrant) 50 mg/mL injection is indicated for the hormonal treatment of locally advanced or metastatic breast cancer in postmenopausal women, regardless of age, who have disease progression following prior anti-estrogen therapy. By stopping some of the actions of estrogen, FASLODEX reduces the amount that is in the body, which has an effect in reducing breast cancer tumour growth.
Rare international cases of false positive increased estradiol levels have been reported in patients receiving FASLODEX, resulting in unnecessary surgery being performed. It could also potentially result in modification of endocrine therapy being initiated. The measurement of low estradiol levels is challenging because of the lack of standardization at low levels in postmenopausal women and the variation in sensitivity/specificity among different immunoassays. Studies suggest that direct immunoassay kits from different manufacturers provide different results and are not always reliable to measure estradiol levels in patients receiving fulvestrant therapy. It is therefore important to recognize the limitations of individual estradiol tests and choose an alternative test method (such as liquid chromatography-mass spectrometry).
Consumers are advised that blood tests to check levels of estradiol (a hormone) may be used during FASLODEX treatment to confirm menopausal status as, with breast cancer patients, this can sometimes change. There have been reports that FASLODEX can interfere with estradiol blood tests and produce incorrect results. Incorrect test results could potentially lead to beneficial therapy being changed or stopped unnecessarily. In rare cases, misinterpreting a patient as premenopausal can lead to unnecessary surgery.
Healthcare professionals are advised that when requesting blood tests that include estradiol, indicate if the patient is on FASLODEX. Caution should be exercised when performing antibody-based estradiol assays for patients taking FASLODEX. The need to carry out a review of the previously reported test results should be considered. Alternative methods such as liquid chromatography-mass spectrometry should be considered.
Healthcare professionals should continue to use estradiol immunoassays for patients not on FASLODEX.
Health Canada in collaboration with AstraZeneca Canada Inc. has updated the FASLODEX Canadian Product Monograph advising of this safety risk.
Please refer to the following website in Health Canada for details:
http://healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/../60590a-eng.php
In Hong Kong, Faslodex Soln for Inj 250mg/5ml (Pre-filled Syringe) (HK-57103) is a pharmaceutical product registered by AstraZeneca Hong Kong Ltd, and is a prescription only medicine. So far, the Department of Health (DH) has not received any adverse drug reaction report related to the product. In view of the Health Canada announcement, letters to inform local healthcare professionals will be issued, and the matter will be discussed by the Registration Committee of the Pharmacy and Poisons Board. DH will remain vigilant on any safety update on the product by other overseas drug regulatory authorities.
Ends/ Wednesday, October 19, 2016
Issued at HKT 15:00
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