KLK3 and neoplasm: In the last decade, circulating tumor cell (CTC) counts has emerged as a biomarker for assessing prognosis and treatment outcome in mCRPC (de Bono et al., 2008), Moreover, post-treatment CTC changes has been associated with mCRPC survival, and it has been shown that CTC count has superior performance to other circulating biomarkers including PSA (Lorente et al., 2016).