In the analysis of the relationship between expression of CAF-related biomarkers and clinical variables, chemotherapy or radiotherapy for primary cancer prior to BM was significantly associated with high expression of PDGFR-β (P = 0.010), α-SMA (P = 0.002), and FSP1/S100A4 (P = 0.012) and marginally associated with Collagen type 1 and FAP-α (P = 0.073 and P = 0.080, respectively, Table 3). Here, PDGFRB is linked to cancer.