We developed a DL-based HE image analyzer called Lunit-SCOPE, in order to identify and quantify various histologic parameters from HE-stained whole slide images. Using the pathology features derived from Lunit-SCOPE, we developed a prediction model for the 21-gene assay RS from Oncotype DX, revealing potential prognostic and predictive biomarkers of ACTx in early-stage HR-positive breast cancers, including SMC and TCGA cohorts. Importantly, for the patients without ACTx, the patients predicted as high-risk through the predicted RS were significantly worse, and the patients with ACTx in the high-risk group had a significantly better prognosis. Moreover, a gene set enrichment analysis biologically validated that the predicted RS was associated with pathways involved in the cell cycle and nuclear grade, which are related with a high risk of recurrence.
Recent advances in DL analysis shed a light on novel approach to understand cancer biology. Growing evidence shows that DL analyses of medical images are clinically reliable tools for diagnosis 15–17. However, the clinical significance of this technology for a predictive biomarker has not been reported yet. Lunit-SCOPE was developed using > 1,000 breast cancer slides, annotated various cell types, and tissue architectures. The preliminary results showed that Lunit-SCOPE accurately predicted tumor proliferation in breast cancer, and a core biologic explanation for how the 21-gene expression assay works in the prediction of high-risk patients would be by evaluating proliferation genes 12. Moreover, Lunit-SCOPE also detects cancer-associated fibroblasts that dirupt the stromal barrier and induce the infiltration of tumor-associated macrophages 18,19, which reflects cancer aggressiveness. Therefore, we hypothesized that Lunit-SCOPE would be able to predict high-risk patients who would benefit from ACTx with clinical significance.
The 21-gene expression assay test includes the gene categories proliferation, estrogen, HER2, invasion, and other cancer-related genes. The five genes related to cancer proliferation had a positive correlation with the predicted RS, based on Lunit-SCOPE, with the pathology images. This suggests that the expression of the genes related to proliferation, cell cycle, and progression ultimately affected the components of the pathology image, which are related to recurrence. All four genes in the estrogen category also had negative correlations with the predicted RS. The Progesterone Receptor (PGR) and Estrogen Receptor 1 (ESR1) are well known genes that influence cancer recurrence. The apoptosis regulator BCL2 was also negatively correlated and is a gene known as a favorable prognostic marker. The directionality of the correlations between the expressions of the recurrence-related genes and the predicted RS indicates that the prediction of this model based on the pathology was consistent with that of the 21-gene expression assay.
There are several limitations in the current study. Firstly, the RS of the training cohort did not have range that was enough to predict RS. As recent clinical trials show that endocrine treatment alone is not inferior to endocrine treatment plus chemotherapy in patients with RS 11 through 25, the most well-validated cutoff of RS for the decision of adding chemotherapy would be 25 8. However, in the current study, only a few patients in training cohort had an RS > 25, and the predicted RS of the training or validation cohort was also dispersed in range that was to the ground truth RS. Therefore, we cannot fully ascertain that this model accurately predicts the RS > 25. Nevertheless, we have shown that a high predicted RS was significantly correlated with a poor prognosis in patients who did not receive ACTx. Another limitation is the selection bias present in retrospective analysis, as patients who did not receive the chemotherapy were related to other clinical factors, such as a poor performance status or poor compliance. Moreover, physicians would choose patients that are clinically high-risk to receive ACTx. This factor could contribute to the worse clinical outcome in the patients with ACTx compared to those without ACTx. To overcome this limitation, a well-designed prospective clinical trial is warranted.
In conclusion, an integrative analysis of Lunit-SCOPE predicts a high risk of recurrence, as well as who would benefit from adjuvant chemotherapy by predicting the RS of the 21-gene expression array in early-stage hormone-positive breast cancer.