KRT18 and neoplasm: Indeed, when examining correlations between the tumor binding potentials of the [11C]-AnxA5-ST tracer and levels of circulating ccK18 fragments in tumor-bearing animals, these were found to be significant (p = 0.023 by Spearman rank correlation, Fig. 4B), as they also were between [11C]-AnxA5-ST binding potentials and plasma K18 (p = 0.007, Fig. 4C).