Monitoring the neoadjuvant therapy response in gynecological cancer patients using FDG PET

We retrospectively evaluated the ability of FDG PET to predict the response of primary tumor to chemotherapy or chemoradiotherapy in patients with gynecological cancer.

FDG PET examinations were performed before and after completion of chemotherapy or chemoradiotherapy in 21 patients with advanced gynecological cancer (uterine cancer, n = 13; ovarian cancer, n = 8). PET imaging was performed at 1 h after injection. Semi-quantitative analysis was performed using the standardized uptake value (SUV) at the primary tumor for both before and after therapy (SUV(before) and SUV(after), respectively). Percent change value was calculated according to the following equation: (SUV(before) - SUV(after) x 100/SUV(before). Based on histopathological analysis of the specimens obtained at surgery, patients were classified as responders or non-responders.

Ten patients were found to be responders and 11 to be non-responders. SUV(after) in responders was significantly lower than that in non-responders (p < 0.005). Taking an arbitrary SUV(after) of 3.8 as the cutoff for differentiating between responders and non-responders, FDG PET showed a sensitivity of 90%, a specificity of 63.6%, and an accuracy of 76.2%. The percent change value in the responders was significantly higher than that in the non-responders (p < 0.0005). Taking an arbitrary percent change of 65 as the cutoff for differentiating between responders and non-responders, FDG PET showed a sensitivity of 90%, a specificity of 81.8%, and an accuracy of 85.7%.

These findings suggest that FDG PET-derived parameters including SUV and especially percent change value may have the potential to predict response to chemotherapy or chemoradiotherapy in patients with advanced gynecological cancer.