Thus, the VEGF-A121 isoform has been uniquely demonstrated as a clear marker of bevacizumab therapy in both plasma and serum, motivating further research on pursuing these isoforms as biomarkers in cancer care, and underscoring the importance of distinguishing between VEGF-A121 and VEGF-A165 instead of determining the concentration of VEGF-A using conventional ELISA. Here, VEGFA is linked to cancer.