P30.02: Accuracy of different risk prediction models and subjective ultrasound assessment to diagnose extraovarian primary peritoneal cancer

Abstract

To evaluate accuracy of risk of malignancy index (RMI), International Ovarian Tumour Analysis (IOTA) models: LR2, ADNEX, Simple Rules (SR), and subjective assessment to diagnose primary peritoneal cancer (PPC) in the absence of typical pelvic tumour. From a group of consecutive patients suspected for ovarian cancer (OC) (symptoms, ascites, elevated cancer antigen (CA) 125) and who underwent laparotomy, 14 had PPC (tumour disseminated on the peritoneum without or with only minimal ovaries involvement). Before surgery all patient underwent standardised transvaginal and abdominal ultrasound examination with predefined definitions (images and videos stored) so to calculate RMI, LR2, ADNEX, SR. A subjective assessment was to discriminate between malignant and benign disease in a 6 point score. High RMI was assessed in all cases. Tumours were classified as malignant (n=3) or inconclusive (n=11) with IOTA-SR. Median value of LR2 was 75.1% (range: 34.7-94.9). Median values of ADNEX model calculations were as follows: risk of malignancy-98.6% (range: 85.6-99.9), risk of stage II-IV OC-89.9%, risk of stage I OC -1.1%, risk of borderline tumour-0.45%, risk of metastatic cancer-7.4%. Once ADNEX model was calculated without CA125, in all cases with ascites the risk of malignancy was still over 91%, while in patients without ascites (n=3) this value was 58-63%. In subjective assessment all patients were suspected for malignancy. There were no pelvic tumours with locules, nor with papillations. Ascites and metastatic tumours in abdominal cavity were detected in 11 and 12 patients respectively. Median ultrasound diameter of ovaries or ovarian involvement was 34mm. Median concentration of CA125 was 928 U/ml (98-7000). In cases with PPC, the RMI, ADNEX model and subjective ultrasound assessment can predict malignancy with a very high accuracy. Evaluation of CA125 should be considered, both as a single diagnostic measure and a part of ADNEX model. IOTA-SR has limited value in diagnosing PPC.