SAN DIEGO — Using ImPrint, an immune-related biomarker, clinicians can identify patients with breast cancer who are likely to respond to neoadjuvant immunotherapy, according to data from the ongoing phase 2 I-SPY2 trial.
Patient selection based on ImPrint class can result in high response rates and spare nonresponders the toxicities of immunotherapy, said Denise M. Wolf, PhD, during her presentation of the study results at the annual meeting of the American Association for Cancer Research (AACR).
“Our results show that patients with ER+/HER2-/ImPrint+ breast cancer have a very high probability of achieving complete response to immunotherapy, whereas those who are ER+/HER2-/ImPrint- have a low probability of responding,” noted Dr. Wolf, PhD, MSc of the University of California, San Francisco (UCSF), in an interview.
She added that, although effective, immunotherapy also carries the risk of serious immune-related toxicities, and knowledge of ImPrint class can help patients and physicians determine whether immunotherapy is a good treatment option. “Many patients will be willing to take the risk of immunotherapy toxicities if their odds of responding are very high, as is the case for ImPrint+ patients, but [are] likely less enthused with a low likelihood of response,” Dr. Wolf said during the interview.
Need for Predictive Biomarkers for Neoadjuvant Immunotherapy
Although neoadjuvant immunotherapy has become the standard treatment for patients with early-stage triple-negative breast cancer (TNBC), chemotherapy remains the mainstay of treatment for patients with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2-) breast cancer. The I-SPY2 clinical trial is the first randomized clinical study to assess the efficacy of immunotherapy in the high-risk population of patients with HR+/HER2-, Dr. Wolf said. Data from this study suggest that a subset of HR+/HER2- patients may also derive substantial benefit from this approach compared with standard chemotherapy.
“We and others have previously observed that a minority of ER+/HER2- breast cancers are enriched for tumor-infiltrating lymphocytes and that high levels of immune-related gene signatures associate with improved survival in this subtype, as well as in TNBC,” noted Dr. Wolf during an interview.
She explained that patients with high-risk ER+/HER2- breast cancer were not responding to any of the experimental agent classes tested in the trial and showed particularly poor outcomes, and that she and her colleagues “wanted to see if immune-oncology agents would impact response in these patients.”
ImPrint, an Immune Expression Signature
Preliminary data from the I-SPY2 trial showed that immune-related gene signatures were associated with pathologic complete response (pCR) in patients with HR+/HER2- breast cancer treated with immunotherapy. This observation allowed investigators to develop a clinically applicable immune classifier, termed ImPrint, to predict response to immunotherapy in this population.
This immune classifier is a 53-gene signature developed using data from the first anti–programmed death-1 (PD-1) arm that included patients treated with pembrolizumab, explained Dr. Wolf.
Performance of ImPrint in Patients With HR+/HER2- Breast Cancer
Dr. Wolf presented new data on the performance of ImPrint in 204 patients with high-risk HR+/HER2- breast cancer from the following five immunotherapy arms of the I-SPY2 trial, at the meeting. These arms included: anti–PD-1, anti–PDL-1 plus PARP inhibitor, anti–PD-1/TLR9 dual immunotherapy, and anti–PD-1 with or without LAG3 inhibitor. Data from 191 patients treated with the current standard of care (paclitaxel followed by adriamycin and cyclophosphamide cytoxan) were included in the analysis as a control.
The pCR in the entire population across these five immunotherapy arms was 33%. The response rate in the control arm was 13.5%.
“The high pCR in the immunotherapy groups is remarkable given the traditionally poor response of HR+/HER2- tumors to standard neoadjuvant chemotherapy,” said Ritu Aneja, PhD, the associate dean for research and innovation at the University of Alabama at Birmingham and a breast cancer expert, who was not involved in the I-SPY2 trial.
When patients were stratified according to ImPrint status, significant differences were observed among the groups. In this analysis, 28% of HR+/HER2- patients were classified as ImPrint positive (likely sensitive) based on ImPrint expression levels in pretreatment mRNA samples, and these individuals achieved pCR rates as high as 76% with immunotherapy.
In comparison, pCR rates were only 16% in ImPrint-negative (likely resistant) patients. The highest response rate was observed in the anti–PD-1/TLR9 dual immunotherapy arm, with a pCR rate of greater than 90% in ImPrint-positive patients. In the control arm, pCR rates were 33% in ImPrint-positive and 8% in ImPrint-negative patients.
“These results suggest that a subset of [patients with] high-risk HR+/HER2- breast cancers is highly sensitive to immunotherapy,” said Dr. Aneja in an interview. “By using a specific and sensitive selection strategy like ImPrint, we may be able to identify patients who can achieve pCR rates similar to what we see with the best neoadjuvant therapies in triple-negative and HER2-positive disease.”
Ability of ImPrint to Predict Long-Term Outcomes
During her talk, Dr. Wolf explained that she and her research team currently do not have sufficient follow-up data to assess the ability of ImPrint to predict long-term outcomes. Therefore, they used the pCR data to predict long-term disease-free survival (DRFS) outcomes. Based on their model, HR+/HER2-/ImPrint+ patients treated with immunotherapy were estimated to have a 91% 5-year DRFS rate, compared with 80% for those receiving standard chemotherapy alone. This represents a 52% reduction in the risk of disease recurrence.
“This suggests not only a higher immediate response rate to therapy but also potential long-term benefits for patients identified as ImPrint+,” Dr. Aneja said, commenting on the significance of the DRFS data, during the interview, She added that the ability to predict longer-term outcomes is a critical advantage in selecting the most effective treatment strategies for patients.
Comparison of ImPrint With Other Biomarkers
The investigators compared ImPrint to other potential biomarkers for immunotherapy response, including MammaPrint (ultra) High2 risk (MP2) and tumor grade. During her talk, Dr. Wolf showed data demonstrating that ImPrint is a more precise predictor of pCR, with higher response rates than either of those other markers.
The pCR rates for MP2 and grade III were 56% and 45%, respectively, which are much smaller than the pCR rates observed for ImPrint+ patients (75%).
“This difference underscores ImPrint’s effectiveness in distinguishing patients who could benefit from immunotherapy, offering a pCR prediction accuracy that is significantly higher than seen with other biomarkers that have been proposed as selection markers for neoadjuvant immunotherapy trials in HR+/HER2- breast cancers, such as MP2 and tumor grade,” said Dr. Aneja, during the interview.