Machine Learning-Based Enhanced MRI Radiomics for PDCD1 Prognostication and Expression Prediction in Breast Cancer

Programmed cell death 1 (PDCD1) is an immune checkpoint inhibitor that plays an important role in immune evasion in breast cancer (BC). In this study, we aimed to evaluate the correlation between PDCD1 expression, immune cell tumor infiltration, and prognosis. In addition, we also developed a predictive model to determine PDCD1 expression levels in patients with BC based on radiomics features extracted from magnetic resonance imaging (MRI).

Clinical data of 1082 patients with BC extracted from The Cancer Genome Atlas (TCGA) and MRI data of 108 patients with BC extracted from The Cancer Imaging Archive (TCIA) were used to determine the correlation between PDCD1 expression levels and the prognosis, clinical stage, survival, and levels of immune cell tumor infiltration in patients with BC. Predictive radiomics features for PDCD1 were extracted by 2 physicians from MRI data. The top 5 predictive features were evaluated and selected to build 2 machine learning models.

The PDCD1 expression levels were significantly higher in tumor tissues from patients with BC (P < .001). High PDCD1 expression levels were associated with improved overall survival, hazard ratio (HR) = 0.63, 95% confidence interval (CI) 0.425-0.934, P = .021. The PDCD1 expression levels showed a significant positive correlation with immune cell infiltration, including CD8 (P < .001) and Treg (P < .001). Both MRI radiomics models demonstrated good accuracy, strong clinical utility, and a high level of consistency in discriminating between low and high PDCD1 expression levels (P > .05).

PDCD1 expression showed a good correlation with prognosis and tumor immune cell infiltration. The MRI radiomics model accurately predicted PDCD1 expression levels and could potentially serve as a noninvasive tool to predict early tumor response to immunotherapy.