Introduction To evaluate the rate of discrepancy between initial diagnosis and surgico-pathological diagnosis in patients treated with neoadjuvant chemotherapy (NAC) followed by interval debulking surgery (IDS) of advanced epithelial ovarian carcinoma (EOC). The second objective was to determine factors associated with diagnosis discrepancy.

Methods The clinical data, disease status, initial cytology/pathology report and final pathology results were extracted from medical records of selected patients who underwent NAC administration followed by IDS from January 2009 to August 2022. Regression analysis was used to investigate the independent factors associated to diagnosis discrepancy.

Results Overall 229 patients underwent IDS. Of these, 11 patients (4.8%) showed diagnostic differences. Patients with CA125 level <200 U/ml had significantly higher discrepancy rate than the group of CA125 level ≥200 U/ml, with 25.0% vs 2.9% (P<0.001) respectively. Furthermore, patients with CEA level >100 ng/ml has a high discrepancy rate of 100%. The CA125/CEA ratio ≤25 was associated with higher discrepancy than patients with ratio >25, with 75.0% vs 4.1% (P<0.001), respectively. The pretreatment cytology, histology, and cytology plus histology results yielded comparable accuracy rates of 96.8%, 91.8%, and 91.7%, respectively (P=0.255).

Conclusion/Implications The discrepancy risk for patients with CA125/CEA ratio ≤25 is unacceptably high, work up for gastro-intestinal malignancies should strongly be recommended. Additionally, either use of cytology or pathology results is reliable for the diagnosis prior to NAC.