In light of concerns that PSA levels simply reflect tumor volume rather than grade, and that they may fail to detect androgen receptor–low or indifferent tumors, PSA measurement remains an excellent biomarker for treatment response, and it is the gold standard for diagnosing biochemical recurrence after primary therapy.29 In our study, we hypothesized that higher grade, more poorly differentiated cancers could be distinguished from indolent tumors on the basis of detection of ctDNA in preoperative plasma. Here, KLK3 is linked to cancer.