Radiotherapy (RTx) remains a cornerstone of the standard-of-care (SOC) for GBM and BCBM but induces IGF1/IGF1R signaling, triggering radio-resistance and recurrence.24 As expected, combining oHSV with RTx significantly increased cytotoxicity across GBM and BC cells, either additively or synergistically, as measured by MTT assay (Fig. 4A, Supplemental Statistics). This evidence concerns the gene IGF1 and breast cancer.