Carboplatin/Paclitaxel +/-Gemcitabine in Treating Patients With Ovarian Epithelial or Fallopian Tube Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells. It is not yet known whether carboplatin and paclitaxel combined with gemcitabine is more effective than carboplatin and paclitaxel alone in treating ovarian epithelial or fallopian tube cancer. PURPOSE: This randomized phase III trial is studying carboplatin and paclitaxel combined with gemcitabine to see how well it works compared to paclitaxel and carboplatin alone in treating patients who have undergone surgery for ovarian epithelial or fallopian tube cancer.