Start of 3rd Chemo Cycle

Hi! everyone. Just want to give an  update on my mom. She started her 3rd cycle yesterday. Still on Oxalipatin, Avastin and Xeloda pills. Blood test came back with good results. Her hemoglobin now is back to 12 (she was 6 prior diagnosis).  CEA Level prior surgery was 189, then went down to 8.6 post op and after 2 cycles, she is now down to 6.4. It is still out of range but I am happy that it had gone down after 2 cycles. My question is .... after how many chemo cycles does CEA show drastic reduction? Does reduction mean that chemo treatments are working ? Can you share your CEA progress so I could have an idea. THank you and keeping you all in my prayers.