Scientists at Weill Cornell Medical College in New York have attached a chemical tag (the isotope lutetium-177) that emits small amounts of radiation onto a monoclonal antibody (J591) that targets prostate cancer cells in bone, soft tissues and circulating blood that carry the protein antigen, prostate-specific membrane antigen (PSMA). Treatment with 177Lu-J591 may be optimally suited to patients with micro-metastatic disease. The developers of this therapy postulate that such treatment in men who have small volume disease not seen on bone scans could even result in a cure for some patients. They specifically refer to men who have had surgery and/or radiation at their primary prostate tumor site who are then experiencing rising PSA levels (biochemical failure) but their bone and CT scans remain negative for metastatic cancer. Results of a Phase II clinical trial of 177Lu-J591 in men who had failed hormonal therapy are summarized in a Jan. 31st, 2014 article from the Prostate Cancer Foundation (PCF). A subsequent Phase II clinical trial at Weill Cornell Medical College and twelve other centers is underway to determine if 177Lu-J591 can delay or prevent overt metastatic disease in men with rising PSA levels after primary treatment and early hormonal therapy but in whom bone and CT scans remain negative. The PSMA antigen is also expressed in other tumors such as liver, breast and kidney; hence this targeted radiotherapy could possibly be used in tumors other than prostate cancer. For further details, see the linked PCF article.