Increased long QT and torsade de pointes reporting on tamoxifen compared with aromatase inhibitors

Abstract

Objective: A prolonged QTc (LQT) is a surrogate for the risk of torsade de pointes (TdP). QTc interval duration is influenced by sex hormones: oestradiol prolongs and testosterone shortens QTc. Drugs used in the treatment of breast cancer have divergent effects on hormonal status.

Methods: We performed a disproportionality analysis using the European database of suspected adverse drug reaction (ADR) reports to evaluate the reporting OR (ROR χ2) of LQT, TdP and ventricular arrhythmias associated with selective oestrogen receptor modulators (SERMs: tamoxifen and toremifene) as opposed to aromatase inhibitors (AIs: anastrozole, exemestane and letrozole). When the proportion of an ADR is greater in patients exposed to a drug (SERMs) compared with patients exposed to control drug (AIs), this suggests an association between the specific drug and the reaction and is a potential signal for safety. Clinical and demographic characterisation of patients with SERMs-induced LQT and ventricular arrhythmias was performed.

Results: SERMs were associated with higher proportion of LQT reports versus AIs (26/8318 vs 11/14851, ROR: 4.2 (2.11-8.55), p<0.001). SERMs were also associated with higher proportion of TdP and ventricular arrhythmia reports versus AIs (6/8318 vs 2/14851, ROR: 5.4 (1.29-26.15), p:0.02; 16/8318 vs 12/14851, ROR: 2.38 (1.15-4.94), p:0.02, respectively). Mortality was 38% in patients presenting ventricular arrhythmias associated with SERMs.

Conclusions: SERMs are associated with more reports of drug-induced LQT, TdP and ventricular arrhythmias compared with AIs. This finding is consistent with oestradiol-like properties of SERMs on the heart as opposed to effects of oestrogen deprivation and testosterone increase induced by AIs.

Trial registration number: NCT03259711.

Keywords: Long QT syndrome; aromatase inhibitors; selective estrogen receptor modulators; sex steroid hormones; torsade de pointes; ventricular arrhythmias.

Conflict of interest statement

Competing interests: JJM (Consultant: Novartis,Pfizer, Bristol Myers Squibb, Takeda). The other authors have nothing to disclose.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Figures

Figure 1.

Forest plot detailing reporting Odds-Ratio (ROR) of suspected adverse drug reactions (ADR) related to acquired long QT, Torsade-de-Pointes, or ventricular arrhythmias between selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs) collected from the European database of suspected ADR reports accessed in 08/2017.

Figure 2.

Synthetic representation of the main study results.