Hi, It prevents the recurrence or metastases of the cancer. Deviry is a synthetic form of female hormone progesterone which is used as a an adjunctive therapy after the primary treatment (radical nephrectomy) to lower the risk that the kidney cancer will come back and also to reduce the metastases (spread) of the cancer. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali, General & Family Physician