In the group with a PSA ≤ 0.2 ng/mL, treatment was continued remarkably frequently despite findings in the PET/CT (6/9; 66.7%), most likely due to a presumably low tumor burden, although patients who were PSA-negative or only had low levels despite a high tumor burden must also be considered here, as can be assumed in the case of the patient who was switched from chemotherapy to RLT or continued chemotherapy. The gene discussed is KLK3; the disease is neoplasm.