I-SPY2 Trial Confirms pCR as Strong Prognostic Biomarker Across Breast Cancer Subtypes and Treatments
Three-year follow-up of 950 patients from the I-SPY2 adaptive trial showed that pathologic complete response after neoadjuvant therapy was associated with an approximately 80% reduction in recurrence risk, with 95% event-free survival at three years. This association held across all molecular subtypes and across nine novel therapeutic combinations. The results reinforce pCR as a robust early endpoint for accelerating drug evaluation in high-risk breast cancer trials.
The original study
Association of Event-Free and Distant Recurrence-Free Survival With Individual-Level Pathologic Complete Response in Neoadjuvant Treatment of Stages 2 and 3 Breast Cancer: Three-Year Follow-up Analysis for the I-SPY2 Adaptively Randomized Clinical Trial.
- Authors
- Yee D, DeMichele AM, Yau C, Isaacs C, Symmans WF, Albain KS, et al.
- Journal
- JAMA oncology
- Type
- Journal Article, Randomized Controlled Trial, Adaptive Clinical Trial
- PMID
- 32701140
Original abstract
IMPORTANCE: Pathologic complete response (pCR) is a known prognostic biomarker for long-term outcomes. The I-SPY2 trial evaluated if the strength of this clinical association persists in the context of a phase 2 neoadjuvant platform trial. OBJECTIVE: To evaluate the association of pCR with event-free survival (EFS) and pCR with distant recurrence-free survival (DRFS) in subpopulations of women with high-risk operable breast cancer treated with standard therapy or one of several novel agents. DESIGN, SETTING, AND PARTICIPANTS: Multicenter platform trial of women with operable clinical stage 2 or 3 breast cancer with no prior surgery or systemic therapy for breast cancer; primary tumors were 2.5 cm or larger. Women with tumors that were ERBB2 negative/hormone receptor (HR) positive with low 70-gene assay score were excluded. Participants were adaptively randomized to one of several different investigational regimens or control therapy within molecular subtypes from March 2010 through 2016. The analysis included participants with follow-up data available as of February 26, 2019. INTERVENTIONS: Standard-of-care neoadjuvant therapy consisting of taxane treatment with or without (as control) one of several investigational agents or combinations followed by doxorubicin and cyclophosphamide. MAIN OUTCOMES AND MEASURES: Pathologic complete response and 3-year EFS and DRFS. RESULTS: Of the 950 participants (median [range] age, 49 [23-77] years), 330 (34.7%) achieved pCR. Three-year EFS and DRFS for patients who achieved pCR were both 95%. Hazard ratios for pCR vs non-pCR were 0.19 for EFS (95% CI, 0.12-0.31) and 0.21 for DRFS (95% CI, 0.13-0.34) and were similar across molecular subtypes, varying from 0.14 to 0.18 for EFS and 0.10 to 0.20 for DRFS. CONCLUSIONS AND RELEVANCE: The 3-year outcomes from the I-SPY2 trial show that, regardless of subtype and/or treatment regimen, including 9 novel therapeutic combinations, achieving pCR after neoadjuvant therapy implies approximately an 80% reduction in recurrence rate. The goal of the I-SPY2 trial is to rapidly identify investigational therapies that may improve pCR when validated in a phase 3 confirmatory trial. Whether pCR is a validated surrogate in the sense that a therapy that improves pCR rate can be assumed to also improve long-term outcome requires further study. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01042379.