The rate at which cancer is found synchronously in the ovaries and endometrium is approximately 3–10% [19]. The Ulbright and Roth criteria proposed in 1986 help in differentiating DPC from MC. We included both DPC and MC patients in our study. However, the clinical factors and survival rate in patients in the two groups were not significantly different. Endometrioid histology of the endometrium (P = 0.002) and ovaries (P = 0.016) and para-aortic lymph node metastasis (P = 0.026) were the risk factors for recurrence, regardless of either DPC or MC.
Almost all SEOCs were evaluated as single primary tumors with metastasis using next-generation sequencing (NGS) in two recently published studies [18, 16, 17]. NGS is an accepted accurate diagnostic tool in various carcinomas, and it is being used increasingly for the diagnosis and treatment of endometrial and ovarian cancers. Genetic analysis using NGS may be accurate in evaluating the characteristics of cancer. However, there was no significant difference in the clinical factors or prognosis between the two groups in those studies. This led to the question of the necessity of classifying two groups and the use of NGS.
The tumor is staged as IA if it is DPC. If it is MC, it is staged as IIIA based on the endometrium or II based on the ovaries. If diagnosed as IA, no additional treatment is required. If diagnosed as IIIA or II, additional treatment is required. Using pathology in distinguishing between DPC and MC may lead to mis-staging; therefore, there are potential risks of wrong management of the patients.
Whether DPC or MC is diagnosed using NGS or pathology, only using the time difference, makes it difficult to determine whether the disease occurred concurrently in both organs or it had metastasized from one organ to the other through an unknown mechanism. Making an accurate differentiation between DPC and MC remains a problem even if the pathology and NGS results are the same. A successful cancer metastasis requires a series of sequential steps such as cancer cell migration, settlement, proliferation, vascularization, etc. This is an inefficient process for cancer cells. Furthermore, even if the NGS results are different, it is impossible to rule out the possibility of either a metastases or DPC. Several reports have shown the cases wherein the genomes of the tumor origin and the metastatic site were different [20–22]. Whether or not a clear-cut difference can be established between DPC and MC using various methods, it does not affect the necessity for the adjuvant treatment.
In this study, the clinical features of 12 patients (5 DPC and 7 MC) with recurrence were assessed, and these data are summarized in Table 3. A non-endometrioid histology and a high FIGO grade were mostly observed in MC. When cancer is diagnosed in the ovary and endometrium synchronously, whether the diagnosis of DPC or MC is made using pathology or NGS, the adjuvant treatment option is determined clinically by the risk factors of each individual patient. Therefore, it would be more important to determine the risk factors and the need for adjuvant treatment rather than how the diagnosis is made.
To increase the reliability of our findings, there is a need for a large multicenter study focusing on the identification of risk factors. This can help improve the prognosis, disease-free survival, and cure rate through aggressive treatment and strong surveillance in patients with synchronous ovarian and endometrial cancer with risk factors for recurrence.