1. 3-year invasive disease-free survival among the PET-based treatment group was 94.8%.

2. There were fewer treatment-related and serious adverse events among patients in the PET-based group compared to the non-PET-based group.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Human epidermal growth factor receptor 2-positive (HER2-positive) breast cancers are associated with a high risk of recurrence and poor prognosis. Although developments in HER2-targeted therapies have improved survival among patients with HER2-positive breast cancer, many patients also receive chemotherapy which may increase the risk for adverse events. This randomized controlled trial aimed to assess the efficacy of chemotherapy-free treatment for patients with HER2-positive breast cancer who showed treatment response on positron emission tomography (PET). The primary outcome was the 3-year invasive disease-free survival rate in patients receiving the dual HER2 blockade regimen, while key secondary outcome was occurrence of treatment-related adverse events. According to study results, the PET-based, pCR-adapted strategy led to significant improvement in 3-year invasive disease-free survival. Although this study was well done, it was limited by its reliance on PET imaging for treatment adaptation.

Click to read the study in The Lancet

Relevant Reading: Pembrolizumab plus Chemotherapy in Advanced Triple-Negative Breast Cancer

In-depth [randomized controlled trial]: Between Jun 26, 2017, and Apr 24, 2019, 376 patients were enrolled across 45 hospitals in 7 countries. Included were female patients ≥ 18 years old with untreated HER2-positive operable breast cancer (≥1.5 cm tumor size) with ≥1 breast lesion on 18F-FDG-PET and an ECOG performance status of 0 or 1. Altogether, 356 patients (71 in docetaxel, carboplatin, trastuzumab, and pertuzumab [group A] vs. 285 in trastuzumab and pertuzumab [group B]) were included in the final analysis. The primary outcome of 3-year invasive disease-free survival was 94.8% (95% confidence interval [CI] 91.4-97.1, p=0.001) in group B. There were more treatment-related adverse events in group A than in group B (grade ≥ 3 62% vs. 33%, serious adverse events 28% vs. 14). Findings from this study suggest that a PET-based, pCR-adapted strategy offers promising outcomes among patients with HER2-positive early breast cancer.

Image: PD

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