My father was diagnosed 4 months ago with stage 4 and 2 different sites of mets on his back. He was put on Lupron, Zyt, and Pred. His PSA of the last reading is less than 0.2 but he started having some lower back pains last night. He said it felt more like muscle pain than spinal pain. He is stubborn though and I would just like to know what the signs are that the back pain is being caused by the cancer.