Yes, losartan is appropriate for this patient
Losartan (an ARB) is an acceptable cardioprotective agent for patients on trastuzumab who develop LVEF decline, though ACE inhibitors are more commonly cited in guidelines. The most recent ESMO 2020 consensus explicitly recommends considering "ACE-Is, ARBs and/or BBs" for cardioprotection in patients with trastuzumab-induced LVEF decline 1.
Evidence Supporting ARB Use
The 2020 ESMO guidelines specifically state that in asymptomatic patients undergoing trastuzumab treatment with an LVEF decrease of ≥10% from baseline or a drop to ≥40% but <50%, clinicians should "consider initiation of cardioprotective treatments (ACE-Is, ARBs and/or BBs), if not already prescribed" 1. This recommendation places ARBs on equal footing with ACE inhibitors for this indication.
Historical Context and Guideline Evolution
While the older 2009 UK NCRI guidelines emphasized ACE inhibitors specifically and provided detailed dosing tables for various ACE inhibitors 2, they did not explicitly mention ARBs. However, this reflects the evidence base available at that time rather than a contraindication to ARB use. The more recent 2020 ESMO consensus represents updated expert opinion incorporating broader cardioprotective strategies 1.
Clinical Algorithm for Cardioprotection
For patients on trastuzumab with LVEF decline:
LVEF drop ≥10% from baseline OR LVEF 40-50%: Continue trastuzumab, initiate cardioprotective therapy (ACE-I, ARB, or BB), obtain cardiology consultation, repeat LVEF in 6-8 weeks 1, 2
LVEF <40%: Hold trastuzumab, initiate cardioprotective therapy, refer to cardiology urgently, repeat LVEF in 3-6 weeks 2
Symptomatic heart failure: Stop trastuzumab immediately, initiate ACE-I or ARB, urgent cardiology referral 2
Important Caveats
The patient should also be on a beta-blocker. The evidence suggests combination therapy with both renin-angiotensin system blockade (ACE-I or ARB) and beta-blockers provides superior cardioprotection compared to monotherapy 3. The 2020 ESMO guidelines recommend considering all three classes together 1.
Close monitoring is essential. Repeat LVEF assessment should occur within 6-8 weeks of initiating cardioprotective therapy to assess response 2. Monthly cardiac biomarkers (BNP/NT-proBNP and troponin) should be considered for ongoing surveillance 1.
ARBs and ACE inhibitors are pharmacologically similar in blocking the renin-angiotensin system, with ARBs often better tolerated due to lower cough incidence. The choice between them is clinically reasonable based on individual patient factors and tolerability.