Evaluation of the correlation between PD-L1 and VEGF-A expression in primary tumors and brain metastases and their association with prognostic parameters

Cancer is generally treatable when detected at an early, localized stage. However, once tumors begin to metastasize, mortality becomes inevitable. While treatment can control many metastatic tumors for extended periods, brain metastases represent a distinct clinical challenge. Inhibition of the PD-1/PD-L1 pathway has been shown to provide benefits ranging from significant regression to sustained remission in patients with advanced solid tumors. Furthermore, low-dose anti-angiogenic (anti-VEGF) therapy has been demonstrated to reprogram the tumor microenvironment (TME) from immunosuppressive to immunostimulatory. Our study included 112 patients diagnosed with both primary tumors and their central nervous system metastases in our institution between 2010 and 2022. A statistically significant relationship was observed between PD-L1 expression in primary and metastatic sites; however, according to concordance measures, the agreement level was mostly weak. Similarly, VEGF expression intensity between primary and metastatic tumors showed a statistically significant association, yet the degree of concordance was very weak. The only statistically significant correlation between PD-L1 and VEGF was a moderate positive correlation between VEGF percentage of staining and PD-L1 TPS in metastatic lesions. Our study demonstrates that the PD L1 marker should be applied to both the primary tumor and the metastatic focus, as different expression levels may be observed in the metastatic focus. To better clarify the relationship between PD-L1 and VEGF immunohistochemical markers, further studies with larger and more homogeneous patient cohorts are warranted.