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The following is a summary of “Pathologic complete response (pCR) rates for patients with HR+/HER2- high-risk, early-stage breast cancer (EBC) by clinical and molecular features in the phase II I-SPY2 clinical trial,” published in the October 2024 issue of Oncology by Huppert et al.  

Hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) early-stage breast cancer (EBC) is a heterogeneous disease, and identifying better biomarkers is essential to optimize therapy.  

Researchers conducted a retrospective analysis to assess pathologic complete response (pCR) and distant recurrence-free survival (DRFS) in patients with HR+/HER2- EBC.  

They analyzed pCR and DRFS rates in 379 patients with HR+/HER2- EBC across 8 neoadjuvant treatment arms in the Investigation of Serial Studies to Predict Your Therapeutic Response with Imaging and Molecular Analysis (I-SPY2) trial. Clinical and molecular features such as age, stage, histology, percentage estrogen receptor (ER) positivity, and molecular signatures (MammaPrint [MP], BluePrint [BP], and ImPrint) were evaluated for links with pCR and DRFS.  

The results showed an observed pCR rate of 17% (379 patients) across treatment arms. The pCR rate was higher in patients with stage II disease compared to stage III (21% vs. 9%, P=0.0013), ductal vs. lobular histology (19% vs. 11%, P=0.049), lower percentage ER positivity (≤66% vs. >66%) (35% vs. 9%, P=3.4E-09), MP-High2 vs. MP-High1 disease (31% vs. 11%, P=1.1E-05), BP-Basal-type versus BP-Luminal-type disease (34% vs. 10%, P=1.62E-07), and ImPrint positive vs. negative disease (38% vs. 10%, P=1.64E-09). Patients with a lower percentage of ER positivity were more likely to have MP-High2 and BP-Basal-type disease. At a median follow-up of 4.8 years, patients who achieved pCR had excellent outcomes, while those who did not had more frequent DRFS events in the MP-High2 and BP-Basal-type groups.  

They concluded that MP-High2, BP-Basal-type, and ImPrint positive signatures identified patients more likely to achieve pCR, suggesting the biomarkers may help optimize treatment selection in HR+/HER2- EBC.  

Source: annalsofoncology.org/article/S0923-7534(24)04070-5/abstract