# A client with HER2-positive breast cancer is starting trastuzumab. Which baseline and follow-up assessment is essential?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391868&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A client with HER2-positive breast cancer is starting trastuzumab. Which baseline and follow-up assessment is essential?

## Option

1. Baseline CBC with differential and weekly monitoring — trastuzumab commonly causes neutropenia, increasing the risk of life-threatening infections during therapy
2. Baseline liver function tests and monthly thereafter — trastuzumab is hepatotoxic, particularly in patients with liver metastases, requiring routine surveillance
3. Baseline LVEF (echo or MUGA) and serial LVEF every 3 months — trastuzumab causes reversible cardiotoxicity, magnified by anthracycline exposure **✔ Correct answer**
4. Baseline PFTs and serial every 3 months — trastuzumab may cause interstitial pneumonitis, requiring early detection to prevent fibrosis

**Correct answer: 3**

## Explanation

Correct (2): Trastuzumab (anti-HER2) causes reversible cardiomyopathy, especially after/with anthracyclines. Baseline + every 3-month LVEF monitoring. Hold for ≥16% absolute LVEF decline or drop below institutional threshold. Often reversible upon discontinuation, unlike anthracycline. (1,3,4) Unrelated.

## In-depth explanation

Memory Tip Trastuzumab = "Tras-2 = HER2 + Heart watch". Reversible cardiotox (unlike doxorubicin permanent). Pertuzumab also HER2; combo CLEOPATRA regimen.

## Clinical scenario

Scenario 48-year-old female with HER2+ breast cancer starting trastuzumab with prior anthracycline exposure.

## Key concepts

- **Trastuzumab (Herceptin)** — Anti-HER2 monoclonal antibody for HER2+ breast/gastric cancer; reversible cardiotox.
- **LVEF monitoring** — Baseline + every 3 months during therapy and after.
- **Reversible cardiotoxicity** — Trastuzumab cardiotox often improves with discontinuation, unlike anthracycline.

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