GPT and cancer: To test if a blood-based CCA could be used as a diagnostic for ALT+ cancer, we performed the CCA on the serum specimens from 35 cases of high-risk neuroblastoma, whose matching tumor specimens had already been tested for ALT [22] by a version of the CCA that uses quantitative PCR for the detection of the CCA products (PCR-CCA) instead of dot blot [43].