We assessed the 27-gene RT-qPCR-based DetermaIO assay and the same score calculated
from RNA sequencing (RNA-seq) data as predictors of sensitivity to immune checkpoint
therapy in the neoTRIPaPDL1 randomized trial that compared neoadjuvant carboplatin/nab-paclitaxel
chemotherapy (CT) plus atezolizumab with CT alone in stage II/III triple-negative
breast cancer. We also assessed the predictive function of the immuno-oncology (IO)
score in expression data of patients treated with pembrolizumab plus paclitaxel (N
= 29) or CT alone (N = 56) in the I-SPY2 trial.RNA-seq data were obtained from pretreatment
core biopsies from 242 (93.8%) of the 258 patients in the per-protocol-population.
The DetermaIO RT-qPCR test, performed in the CAP/CLIA-accredited laboratory of Oncocyte
Corp., was available for 220 patients (85.3%). A previously established threshold
was used to assign DetermaIO-positive versus DetermaIO-negative status. Publicly available
microarray data were used from I-SPY2.IO scores calculated from RNA-seq and RT-qPCR
data were highly concordant. In neoTRIPaPDL1, DetermaIO-positive cancers (N = 92,
41.8%) had pathologic complete response (pCR) rates of 69.8% and 46.9% in the CT +
atezolizumab and CT arms, respectively. In DetermaIO-negative cases, pCR rates were
similar in both arms (44.6% vs. 49.2%; interaction test P = 0.04). PDL1 protein expression
and stromal tumor-infiltrating lymphocyte count were not predictive of differential
benefit from atezolizumab. In I-SPY2, IO-positive cancers (45.9%) had pCR rates of
85.7% and 16%, with and without immunotherapy, respectively. In IO-negative cancers,
pCR rates were 46.7% versus 16.1%.DetermaIO identified patients who benefited from
neoadjuvant immunotherapy resulting in improved pCR rate, independently of PDL1.
