Prognostic analysis of peritoneal washing cytology during interval debulking surgery in advanced ovarian cancer

Abstract

Background

Interval debulking surgery (IDS) following neoadjuvant chemotherapy is a treatment option for advanced ovarian cancer. Optimal surgery is required for better survival; however, while peritoneal washing cytology (PWC) has been identified as a prognostic factor, its comprehensive assessment during IDS remains unexplored. Therefore, we aimed to evaluate PWC efficacy during IDS, alongside other factors including residual disease and the modeled cancer antigen 125 (CA-125) ELIMination rate constant K (KELIM), by retrospectively reviewing the medical records of 25 patients with advanced ovarian cancer underwent neoadjuvant chemotherapy and IDS between January 2017 to June 2023.

Results

Twelve (48.0%) patients were PWC-positive, and the remainder were PWC-negative. PWC was performed at laparotomy during IDS, after which five (41.7%) PWC-positive and four (30.8%) PWC-negative patients received bevacizumab, an anti-vascular endothelial growth factor monoclonal antibody, for maintenance treatment. Four (33.3%) PWC-positive and 10 (76.9%) PWC-negative patients received poly adenosine diphosphate (ADP)-ribose polymerase inhibitors. In patients who received bevacizumab and poly ADP-ribose polymerase inhibitors, overall survival and progression-free survival did not significantly differ between those who were PWC-positive and PWC-negative (p = 0.27 and 0.20, respectively). Progression-free survival significantly differed between those with favorable and unfavorable CA-125 KELIM (p = 0.02). Multivariate analysis indicated that optimal surgery and favorable CA-125 KELIM were associated with better progression-free survival (p < 0.01 and 0.02, respectively), with only optimal surgery associated with better overall survival (p = 0.04).

Conclusions

A positive PWC at IDS was not associated with survival in advanced ovarian cancer. Our findings indicate that although PWC status at IDS should be one of the factors determining survival in patients with advanced ovarian cancer, recent improvements in maintenance therapy may make the combination of CA-125 KELIM and PWC status a more useful prognostic factor in selecting treatment after IDS. Further studies are needed to validate these results, highlighting the potential importance of maintenance treatment after IDS and the need for further research to validate the clinical significance of a positive PWC.

Background

Ovarian cancer is the most lethal gynecologic malignancy, with most patients diagnosed at advanced stages [1]. Achieving optimal surgical debulking is required for improving overall survival (OS) and progression-free survival (PFS); however, primary debulking surgery is potentially challenging, given that many of these patients present with large disease burdens, multiple metastases, or concurrent comorbidities. Neoadjuvant chemotherapy (NAC) followed by interval debulking surgery (IDS) is an alternative treatment for advanced ovarian cancer to achieve complete cytoreduction with no macroscopic residual disease (RD) [1, 2]. Complete RD removal is associated with a better survival outcome when performed using either primary debulking surgery (PDS) or an NAC/IDS approach [2]. No difference in survival rates has been reported in terms of reduced morbidity in patients treated with NAC compared with those who underwent PDS [3, 4].

Peritoneal washing cytology (PWC) can provide useful clinical information, offering insights into the prognosis of patients with advanced ovarian cancer who have undergone NAC/IDS [5, 6]. Recent studies have evaluated maintenance therapy strategies for advanced ovarian cancer following NAC/IDS; these therapies, including bevacizumab (BEV), an anti- vascular endothelial growth factor monoclonal antibody, and poly adenosine diphosphate-ribose polymerase inhibitors (PARPi), such as olaparib and niraparib, have revealed improved PFS outcomes [7,8,9]. Additionally, You et al. highlighted the clinical utility of calculating the cancer antigen 125 (CA-125) decline percentage, specifically the CA-125 ELIMination rate constant K (CA-125 KELIM), as a means to assess chemosensitivity during NAC [10]. This calculation holds the potential to assist clinicians in decision-making regarding the feasibility of IDS.

Although it is known that the faster the serum CA-125 level decreases in a patient with advanced ovarian cancer, the better the outcome, using it as a numerical value in actual clinical practice has not been possible. Notably, some patients with advanced ovarian cancer may not have elevated serum CA-125 levels, depending on the histology. However, in many cases of advanced ovarian cancer, serum CA-125 levels are a biomarker for chemotherapy. Based on these developments in ovarian cancer treatment and the emergence of markers for detecting chemosensitivity, we aimed to evaluate the effectiveness of PWC during IDS in relation to prognosis, combined with other factors, including RD and CA-125 KELIM, to gain a comprehensive understanding of its clinical significance.

Methods

Study design and ethical approval

We retrospectively reviewed the medical records of 25 patients with advanced ovarian cancer who underwent NAC/IDS at our institute between January 2017 and June 2023. We excluded patients who received PDS without NAC/IDS, those who underwent only debulking surgery or chemotherapy, those who did not receive treatment, those who did not have a confirmed diagnosis, and those with double primary cancer. The study’s retrospective design was approved by the Institutional Review Board of Teikyo University. The requirement for informed consent was waived owing to our study’s retrospective design.

Diagnosis and treatment decision

Ovarian cancer was diagnosed using exploratory laparoscopy or laparotomy, image-guided biopsy, and peritoneal cytology combined with imaging findings and tumor markers. The decision to perform NAC/IDS was based on primary tumor status and the presence of metastasis. NAC regimens primarily consisted of taxane and platinum-based combinations. IDS was considered for patients who achieved either a complete response or a partial response, assessed in accordance with the modified Response Evaluation Criteria In Solid Tumors (RECIST) criteria. Patients with disease progression despite NAC were deemed ineligible for IDS.

CA-125 assessment and CA-125 KELIM calculation

CA-125 concentration was measured prior to treatment, at each NAC cycle, immediately before IDS, and at each adjuvant therapy session. The standardized CA-125 KELIM was calculated using Biomarker Kinetics (https://www.biomarker-kinetics.org/CA-125-neo) [10]. To establish CA-125 KELIM, at least three available CA-125 values during the initial 100 days of NAC was required. A standardized CA-125 KELIM ≥ 1 was defined as favorable CA-125 KELIM, associated with heightened primary tumor chemosensitivity and improved prognosis, whereas a standardized CA-125 KELIM < 1 indicated unfavorable CA-125 KELIM, associated with reduced primary tumor chemosensitivity and a poorer prognosis [10].

PWC procedures and cytological evaluation

During IDS laparotomy, the presence of free abdominal fluid in the pelvis or abdominal cavity prompted ascites aspiration for cytological evaluation. In cases where ascites were absent, peritoneal washing of the pouch of Douglas was performed using approximately 20.0 mL of saline, and the collected fluid was subjected to peritoneal washing cytology (PWC). In addition, sufficient saline was added to the abdominal cavity to collect as many floating cells as possible from the entire cavity, which were agitated and collected as PWCs. As the pouch of Douglas was considered to contain the most essential suspended cells, it was first carefully cleaned before samples were collected from the entire intraperitoneal cavity. We defined the criteria for positive PWC as class 4 or 5. All reactive mesothelial cell contamination, endometriosis, or atypical cells due to blood or inflammation are excluded from the diagnosis, which is determined by several skilled cytologists who are positive for findings that they strongly believed were cancer cells in tumorigenesis. Standard IDS procedures included total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, and metastasis resection for RD reduction. Routine pelvic and paraaortic lymph node dissections were not performed. The colon, intestine, diaphragm, liver, and pouch of Douglas were directly visualized and palpated to detect dissemination. Surgical procedures such as bowel resection, partial hepatectomy, splenectomy, or diaphragm stripping were performed when tumors were observed. Optimal cytoreduction post-IDS was defined as RD < 1 cm in its largest diameter, whereas suboptimal cytoreduction was categorized as RD ≥ 1 cm. The selection of adjuvant therapy was determined based on RD, PWC, or homologous recombination deficiency (HRD) status (Fig. 1).

Fig. 1

Treatment flow chart at our institute. HRD, homologous recombination deficiency; IDS, interval debulking surgery; NAC, neoadjuvant chemotherapy; PDS, primary debulking surgery; PWC, peritoneal washing cytology

Data collection and analysis

Medical and surgical data, including age, tumor histology, stage, completion of IDS, maximal tumor size, PWC, CA-125 concentration, HRD status, germline BRCA1/2 mutation status, and post-IDS use of BEV or PARPi, were extracted from relevant medical and surgical records. All cases were staged in accordance with the 2014 International Federation of Gynecology and Obstetrics (FIGO) staging system [11]. Chi-squared, Fisher’s exact, and Student’s t- tests were used for analysis of clinical characteristics. Survival curves were plotted using the Kaplan–Meier method and compared using a log-rank test. Multivariate analysis was performed using Cox proportional hazard models. OS was defined as the interval from the first date of therapy to the date of death. PFS was defined as the interval from the first date of therapy to progression or death. A p-value < 0.05 was considered statistically significant. All statistical analyses were performed using JMP version 16.0.0 (SAS Institute, Cary, NC) software.

Results

Patient characteristics

Patient characteristics are summarized in Table 1. Twenty-five patients were included in our study, of whom 12 (48.0%) were PWC-positive during IDS, and 13 (52.0%) were PWC-negative. The median age at the initial treatment in both these two groups was 57 years (range, 45–81 and 39–78 years, respectively). Most patients received combination paclitaxel and carboplatin therapy (TC therapy) for NAC, except for one patient who received dose-dense TC therapy. In both PWC-positive and -negative patients, the median number of NAC cycles administered was five (3–6 and 3–7 cycles, respectively), with no significant difference (p = 0.15). We observed no significant difference in terms of age, histology, FIGO stage, tumor size, or the use of BEV or PARPi. Optimal debulking was achieved in nine (75.0%) and 11 (84.6%) patients with positive and negative PWC, respectively, with no significant difference (p = 0.55). Favorable CA-125 KELIM was more frequently observed in patients with negative PWC than in those with positive PWC (p = 0.02). Among patients with positive PWC, six had undergone HRD testing, and three (50.0%) showed a positive HRD status. Among patients with negative PWC, eight had undergone HRD testing, and all (100%) patients showed a positive HRD status (p = 0.02). Germline BRCA1/2 testing was performed in six patients with positive PWC and in 11 patients with negative PWC, of whom three (50.0%) and six (54.5%) had germline BRCA1/2 mutation, respectively (p = 0.86).

Table 1 Study patient characteristics

Survival analysis

The median OS of patients with positive PWC and those with negative PWC was 30 (range, 11–58) months and 26 (range, 7–54) months, respectively (Fig. 2a). No significant difference was observed between the groups (p = 0.27). The median PFS of patients with positive PWC and those with negative PWC was 23 (range, 10–58) months and 19 (range, 7–54) months (Fig. 2b). No significant difference was observed between the groups (p = 0.20). The median OS of patients with favorable CA-125 KELIM and those with unfavorable CA-125 KELIM was 28.5 and 26 months, respectively (p = 0.08, Fig. 3a). The median PFS of patients with favorable CA-125 KELIM and those with unfavorable CA-125 KELIM was 31 and 15 months, respectively (p = 0.02, Fig. 3b).

Fig. 2

OS and PFS in patients with positive and negative PWC. a OS in patients with positive and negative PWC. b PFS patients with positive and negative PWC. OS, overall survival; PFS, progression-free survival; PWC, peritoneal washing cytology

Fig. 3

OS and PFS in patients with favorable and unfavorable CA-125 KELIM. a OS in patients with favorable and unfavorable CA-125 KELIM. b PFS in patients with favorable and unfavorable CA-125 KELIM. CA-125 KELIM, CA-125 ELIMination rate constant K; OS, overall survival; PFS, progression-free survival; PWC, peritoneal washing cytology

Surgical impact on survival

In cases of optimal surgery, no difference in OS and PFS was observed in relation to PWC status (p = 0.19 and 0.24, respectively; Fig. 4a, b). No significant differences in OS or PFS were observed in relation to KELIM status (p = 0.33 and 0.08, respectively; Fig. 5a, b). In cases of suboptimal surgery, no differences in OS and PFS were observed in relation to PWC status (p = 0.32 and 0.50, respectively; Fig. 6a, b). However, a significant difference was observed in PFS in relation to KELIM status (p < 0.05, Fig. 7b), with no significant difference in OS (p = 0.08, Fig. 7a). CA-125 KELIM and PWC status were then assessed in combination: PFS was inferior in cases with positive PWC and unfavorable CA-125 KELIM, whereas cases with favorable CA-125 KELIM had a relatively good prognosis regardless of PWC status (Fig. 8a). To exclude the effect of BEV treatment on PWC status, we performed a separate analysis of cases with and without BEV introduced into chemotherapy. Interestingly, when cases with BEV introduced into chemotherapy were excluded, the difference in PFS was significant (p < 0.01) (Fig. 8b).

Fig. 4

OS and PFS in patients with positive and negative PWC among those who underwent optimal surgery. a OS in patients with positive and negative PWC among those who underwent optimal surgery. b PFS in patients with positive and negative PWC among those who underwent optimal surgery. OS, overall survival; PFS, progression-free survival; PWC, peritoneal washing cytology

Fig. 5

OS and PFS in patients with favorable and unfavorable CA-125 KELIM among those who underwent optimal surgery. a OS in patients with favorable and unfavorable CA-125 KELIM among those who underwent optimal surgery. b PFS in patients with favorable and unfavorable CA-125 KELIM among those who underwent optimal surgery. CA-125 KELIM, CA-125 ELIMination rate constant K; OS, overall survival; PFS, progression-free survival; PWC, peritoneal washing cytology

Fig. 6

OS and PFS in patients with positive and negative PWC among those who underwent suboptimal surgery. a OS in patients with positive and negative PWC among those who underwent suboptimal surgery. b PFS in patients with positive and negative PWC among those who underwent suboptimal surgery. OS, overall survival; PFS, progression-free survival; PWC, peritoneal washing cytology

Fig. 7

OS and PFS in patients with favorable and unfavorable CA-125 KELIM among those who underwent suboptimal surgery. a OS in patients with favorable and unfavorable CA-125 KELIM among those who underwent suboptimal surgery. b PFS in patients with favorable and unfavorable CA-125 KELIM among those who underwent suboptimal surgery. CA-125 KELIM, CA-125 ELIMination rate constant K; OS, overall survival; PFS, progression-free survival

Fig. 8

Combined analysis of favorable and unfavorable CA-125 KELIM and PWC status in patients. a PFS in patients divided by favorable and unfavorable CA-125 KELIM and PWC status. b PFS in patients and those without BEV treatment, divided by favorable and unfavorable CA-125 KELIM and PWC status. PFS, progression-free survival; CA-125 KELIM, CA-125 ELIMination rate constant K; PWC, peritoneal washing cytology; BEV, bevacizumab

Multivariate analysis

The results of multivariate analysis for PFS and OS are shown in Table 2. A favorable CA-125 KELIM (hazard ratio [HR] 0.17, 95% confidential interval [CI] 0.04–0.71; p = 0.02) and optimal surgery (HR 0.15, 95% CI 0.04–0.57; p < 0.01) were identified as independent favorable predictors for PFS. We observed no significant difference observed in terms of the use of BEV or PARPi, and the status of PWC. Moreover, optimal surgery was identified as an independent prognostic factor for better OS (HR 0.09, 95% CI 0.01–0.97; p = 0.04). Finally, we observed that a favorable CA-125 KELIM was not associated with better OS (HR 0.37, 95% CI 0.01–10.6; p = 0.57).

Table 2 Multivariate analysis of PFS and OS in patients who received NAC followed by IDS

Discussion

In this study, we retrospectively analyzed data from 25 patients with advanced ovarian cancer who underwent NAC/IDS at our institution, and we investigated the prognostic significance of PWC in NAC-treated patients. While previous studies have highlighted the improved prognosis with NAC/IDS and the importance of optimal debulking [1, 2, 12], our findings deviate from previous reports [5, 6, 13] by indicating differences in OS and PFS between patients with positive and negative PWC, but not significant, regardless of RD status. One possible explanation for this difference is the incorporation of adjuvant therapy post-IDS, including BEV or PARPi, which may have improved outcomes by suppressing malignant cell growth and peritoneal metastasis [7, 14].

Floating cells in ascites may no longer correlate with prognosis, given that BEV, an angiogenesis inhibitor, can suppress the growth of peritoneal seeding foci in advanced ovarian cancer [15]. Previous studies reporting the clinical efficacy of PWC in advanced ovarian cancer were conducted before the approval of maintenance treatments such as BEV or PARPi. These maintenance therapies have been reported to significantly enhance PFS [7,8,9, 16], potentially mitigating cancer progression even in the presence of remaining malignant cells in the abdomen, reflected as positive PWC. Compared with earlier PWC-related research, our study demonstrated extended PFS, whereas OS remained similar to other studies, likely owing to the clinical efficacy of maintenance therapy. Furthermore, we identified optimal debulking as the sole parameter associated with improved OS and PFS. However, favorable CA-125 KELIM correlated with better PFS but not OS, especially in cases of suboptimal surgery. In combination with PWC status, CA-125 KELIM is considered to play a role in indicating tumor chemosensitivity. Nevertheless, NAC might induce platinum-resistant clones, potentially leading to platinum-resistant recurrence [17], which could explain the OS outcomes associated with CA-125 KELIM. These results highlight the clinical significance of debulking in ovarian cancer. In contrast to previous reports [7,8,9], we did not observe any association between the administration of BEV or PARPi and improved PFS, likely owing to the small sample size.

However, our study has several limitations. First, this was a retrospective single-institutional study with limited sample size. Therefore, further analysis with larger cohorts is necessary to validate the significance of PWC status during IDS. Second, not all study patients underwent HRD or germline BRCA1/2 mutation testing, which may have introduced bias. Finally, criteria for administering BEV or PARPi remain unestablished, and while our institution follows a treatment flow chart for adjuvant therapy, clinicians retain discretion in the use of these maintenance treatments. Nevertheless, our results highlight the potential clinical benefit of determining the PWC status, especially in the context of maintenance treatments, including BEV or PARPi, and may paradoxically support the potential efficacy of maintenance therapy post-NAC/IDS.

Conclusions

In conclusion, our findings indicate that PWC status during IDS does not correlate with survival in patients with advanced ovarian cancer. Even in cases of positive PWC, maintenance treatment may mitigate disease progression. The combined PWC status and CA-125 KELIM indicator could be a tool for correctly assessing chemosensitivity after IDS. Further analyses are required to validate these findings.