Abstract： Objective To investigate the changes of CA125 between primary cytoreductive surgery and interval debulking surgery for prediction the rate of optimal interval cytoreductive surgery and prediction the recurrence and the prognosis in patients with epithelial ovarian cancer.Methods A total of 39 cases with suboptimal primary cytoreductive surgery admitted from Jan.1996 to Jan.2009 were retrospectively analyzed.The median age of patients was 56 years( range:41 -68 years).Based on the changes in CA125level between primary cytoreductive surgery and interval debulking surgery,all cases were divided into four groups,group A (CA125 reduced to normal after primary cytoreductive surgery,n=6),group B (CA125reduced to normal after 1 - 2 cycles of chemotherapy,n =11 ),group C ( CA125 reduced to normal after 3 -4 cycles of chemotherapy,n =14),and group D ( CA125 did not reduced to normal after the chemotherapy,n =8 ), and all received platinum-based chemotherapy.The response to chemotherapy evaluated by pathological examination versus CA125 level,and recurrence and prognoses were also analyzed.Results ( 1 )The rate of optimal interval cytoreductive surgery in group A,B,C and D were 6/6,8/11,9/14 and 2/8respectively,in which there were statistically different between group A or B and group D (P ＜0.05).(2)The clinical benefit rates evaluated by the pathological examination in group A,B,C and D were 4/6,4/11,5/14 and 0,respectively and there were statistically different between group A and group D (P =0.030).( 3 ) There was significant difference in the recurrence rate between group A and group D (3/6 vs.8/8,P =0.024),while there were not significant differences between group B or C and group D ( all P ＞ 0.05 ).The rate of drug-resistant recurrence in group A,B,C and D were 1/6,3/11,5/14 and 7/8,respectively,in which there were significant differences between group A,B or C and group D ( all P ＜ 0.05 ). ( 4 ) The median progression-free survival (PFS) for patients in group A,B,C and D were 32,10,18 and 3 months,respectively,in which there were significant differences in the PFS between group A,B or C and group D (P =0.012,P =0.003,P =0.032 ).The median overall survival (OS) were 44,45,44 and 16 months,respectively.There were significant differences in the OS between group A,B or C and group D ( P =0.022,P =0.004,P =0.000 ).Conclusion The change of CA125 between primary cytoreductive surgery and interval debulking surgery may be predict the recurrence type and the prognosis in patients with epithelial ovarian cancer.