In the current study, data of patients with OCCC who undergone surgery in SEER database were used for the analysis of risk factors. Nomograms were constructed to assess the 3- and 5-year CSS and OS based on the identified prognostic factors. Favorable discrimination and calibration were observed from C-index, calibration curves and DCA curves in both training and validation sets, indicating excellent performances of the nomograms. Moreover, risk scores generated from the nomograms were applied to successfully build a risk stratification system.
Our study identified six independent prognostic factors for OS: age, tumor laterality, organ metastasis, LN dissected, stage and chemotherapy. These factors were also significantly impact CSS, except for age. Generally, patients at an older age would be more likely to present worse survival outcomes due to lower immune response. However, we observed that patients younger than 50 years were associated with poor prognosis. One of the possible explanations may be the relatively conservative surgical mode for patients who wanted to preserved fertility. In addition to age, the relationship between other demographic characteristics (such as race) and prognosis were explored.
Systematic lymphadenectomy was regarded as an important part of treatment guidelines for patients with EOC considering the prognostic value of LN status. We observed that patients with more than 10 lymph nodes removed were associated with better prognosis. A 10-lymph node cutoff was defined as adequate lymphadenectomy according to the Gynecologic Oncology Group criteria. Several retrospective studies have demonstrated favorable survival outcomes of systematic lymphadenectomy on early-stage OCCC[13–15]. In a combined exploratory analysis of three prospectively randomized phase III multicenter trials, du et al. reported that lymphadenectomy offered benefit to patients with advanced OC who received complete intraperitoneal debulking. However, another study did not observe significant improvement in survival of advanced OCCC with systematic retroperitoneal lymphadenectomy. It is worth noting that, LN status was not a prognostic factor in our study. Therefore, the role of lymphadenectomy on the whole cohort of OCCC patients required further investigation.
Chemotherapy is important in the management of EOC, especially for high grade cases, while the role of chemotherapy for patients with OCCC remain controversial. It was reported that the response rate of OCCC to conventional platinum was much lower than serous type in the first-line setting. Published studies mainly focused on the performance of chemotherapy on early-stage cases[20–22]. In our study, chemotherapy was significantly associated with OS and CSS, implying its value in improving survival outcomes. Toru and his group carried out a randomized phase III trial (JGOG3017/GCIG Trial) to make a comparison between two chemotherapy regimens for OCCC. They demonstrated that irinotecan plus cisplatin and paclitaxel plus carboplatin were both well tolerated with no significant difference in survival benefit.
Several studies have reported better performance of nomogram model than conventional staging systems and proposed it as a promising tool for prognosis evaluation[24–26]. The nomograms developed in our study also presented better prediction capacity than AJCC 7th staging system. The nomogram model enables risk stratification of patients, thus facilitating the determination of personalized treatment plans and follow-up schedule. Considering the chemo-resistant feature of OCCC, efforts have been made to explore precision medicine based on molecular profile, such as drugs targeting ARID1A-deficient OCCC patients. It may be feasible to use nomogram model to select candidates for clinical trials.
It should be noted that several limitations existed in our study. First, detailed information about chemotherapy and radiotherapy as well as surgical procedures were unavailable. Data about the recurrence and reoperation were also unavailable in SEER database. Second, selection bias was inevitable due to the retrospective nature. Third, the nomogram model only received internal validation. External validation on cohorts from other countries and prospective randomized clinical trials were necessary to confirm its performance.