Objective: To evaluate the ability of a risk of malignancy index (RMI), based on a serum CA125 level, ultrasound findings and menopausal status, to discriminate a benign from a malignant pelvic mass and to discriminate early stage (Figo Stage I) from Stages II, III and IV of ovarian cancer.
Design: A prospective study.
Setting: Department of Gynaecology, Trondheim University Hospital, Trondheim, Norway.
Participants: One hundred and seventy-three women, 30 years or older, consecutively admitted between February 1992 and February 1994 for primary laparotomy of a pelvic mass.
Main outcome measures: The sensitivity, specificity and positive predictive value of serum CA125 level, ultrasound findings and menopausal status, separately and combined into the RMI, to diagnose ovarian cancer.
Results: The RMI was more accurate than any individual criterion in diagnosing cancer. Using a RMI cut-off level of 200 to indicate malignancy, the RMI derived from this dataset gave a sensitivity of 80%, specificity of 92% and positive predictive value of 83%. Applying RMI criteria developed by others, the following test performance was found: sensitivity 71%, specificity 96% and positive predictive value 89%. For the Stages II, III and IV of ovarian cancer the sensitivity increased to approximately 90% without any substantial loss in specificity.
Conclusions: The risk of malignancy index is able to correctly discriminate between malignant and benign pelvic masses. It is a scoring system which can be introduced easily into clinical practice to facilitate the selection of patients for primary surgery at an oncological unit.