The aim of this study was to examine the relationship between the reduction of maximum standardized uptake values (SUVmax) in (18)F-FDG-PET/CT to histopathological changes obtained with neoadjuvant chemotherapy (NACT) in advanced epithelial ovarian cancer (EOC). We wanted to evaluate whether (18)F-FDG-PET/CT is useful for identifying patients who will not respond to NACT and would therefore benefit from second-line chemotherapy instead of interval debulking surgery (IDS).

Twenty-six primarily inoperable EOC patients treated with NACT were enrolled in this study. (18)F-FDG-PET/CT imaging was performed before diagnostic laparoscopy and after three to four NACT cycles. The relationship between the decrease in omental SUVmax from before to after NACT with omental histopathological response was examined in samples taken from the corresponding anatomical sites during IDS. Patients were divided into three groups according to chemotherapy-induced histopathological changes. Serum CA125 and HE4 halftimes during NACT as well as Ki-67 antigen expression in IDS samples were determined.

The median omental SUVmax change during NACT was -64% (range-16% to -84%), and it was associated with histopathological response (p=0.004, OR 0.9, CI 0.84-0.97). A SUVmax decrease of less than 57% identified histopathological non-responders. Progression-free survival (PFS) differed between the poor, moderate and good histopathological response groups (0.9year vs 1.2years vs 1.4years, respectively, p=0.05). The SUVmax change was not associated with PFS.

(18)F-FDG-PET/CT was able to identify patients who would not respond to NACT. To obtain a histopathological response in EOC, a substantial metabolic response in (18)F-FDG-PET/CT is necessary.