Purpose
Our goal was to determine whether tumor radiosensitivity is associated with activation of the immune system across all tumor types as measured by two gene expression signatures (GES).
Methods
We identified 10,240 genomically profiled distinct solid primary tumors with gene expression analysis available from an institutional de-identified database. Two separate GES were included in the analysis, the radiosensitivity index (RSI) GES (a 10-gene GES as a measure of radiosensitivity), and the 12-chemokine (12-CK) signature (a 12-gene GES as a measure of immune activation). We tested whether the RSI and 12-CK were associated with each other across all tumor samples, and in an exploratory analysis, their prognostic significance in predicting distant metastasis-free survival (DMFS) among a well-characterized, independent cohort of 282 early-stage breast cancer cases treated with surgery and post-operative radiation alone without systemic therapy. The lower the RSI score, the higher the tumor radiosensitivity; whereas, the higher the 12-CK score the higher the immune activation.
Results
Using an RSI cut-point of ≤0.3745, RSI-low tumors (n=4,291, 41.9%) had a significantly higher median 12-CK GES value (0.54 [range −0.136,1.095]) compared with RSI-high tumors (−0.17 [−0.82,0.42]; p<0.001) across all tumor samples, indicating that radiosensitivity is associated with immune activation. In an exploratory analysis of early stage breast cancer cases, a multivariable model with patient age, RSI and 12-CK provided a strong composite model for DMFS (p=0.02), with RSI (HR 0.63 [95%CI 0.36,1.09]) and 12-CK (HR 0.66 [0.41,1.04]) each providing comparable contributions.
Conclusions
Tumor radiosensitivity is associated with immune activation as measured by two GES.