Negative peritoneal washing cytology during interval debulking surgery predicts overall survival after neoadjuvant chemotherapy for ovarian cancer

OBJECTIVE: Optimal debulking in interval debulking surgery (IDS) after neoadjuvant chemotherapy (NAC) has been reported as a prognostic factor for patients with ovarian cancer. However, the identification of microscopic residual disease (MRD) using visualization and palpation is subjective. Peritoneal washing cytology (PWC) during IDS is an easy-to-implement, objective approach for assessing disease status, although its clinical relevance and association with MRD is not known. The aim of this study was to evaluate the efficacy of PWC during IDS. METHODS: In total, 164 patients diagnosed with ovarian cancer at our institution were retrospectively evaluated, including 64 who had received NAC. Seventeen patients had undergone an exploratory laparotomy followed by NAC, while the remaining patients were diagnosed based on imaging, peritoneal cytology, and tumor markers. The PWC was performed before intraperitoneal observation at laparotomy during IDS. RESULTS: NAC-treated patients had stage III–IV disease. IDS was performed in 78.1% of NAC-treated patients. Seventeen patients (26.6%) were PWC-negative and 33 patients (51.6%) were PWC-positive. Fourteen patients (21.9%) had progressive disease and were ineligible for IDS. The median overall survival of the PWC-negative, PWC-positive, and non-IDS groups was 47, 18, and 5 months, respectively. The differences were significant (p<0.01). PWC was an independent prognostic factor in the multivariate Cox regression analysis (p<0.001). CONCLUSION: PWC during IDS may be a prognostic factor for NAC-treated patients with ovarian cancer. PWC may be more useful than visualization and palpation in IDS for determining the presence of MRD.