Published preclinical studies have demonstrated that , unlike standard paclitaxel and other chemotherapeutic agents that enhance radiation killing by a factor of 1.5 to 2.0 , OPAXIO increases tumor specific radiation cell kill by a factor of 7.2 to 8.4-fold ( Milas Luka et al , Poly ( L-glutamic acid ) -paclitaxel conjugate is a potent enhancer of tumor radiocurability , Int 'l J. Radiat .