Prognostic factors for malignant tumors arising from mature cystic teratomas: A study involving the Kansai Clinical Oncology Group (KCOG-G1305s study)

Background : Current evidence regarding the prognostic factors of malignant tumors arising from mature cystic teratomas (MT-MCTs) and effective treatments is insufficient. Aim : This study aimed to identify the risk factors for malignant tumors arising from mature cystic teratomas (MT-MCTs) of the ovary. Methods : Tumor samples diagnosed as MT-MCTs were collected from 13 institutions participating in the Kansai Clinical Oncology Group. Based on the clinicopathological features and prognoses of the tumors, the risk factors for progression and death were statistically assessed via univariable and multivariable analyses. Results : Among the 60 tumor samples collected, 56 were diagnosed as MT-MCTs; the exclusion of four samples was based on the results of a central pathological review. Nine histological types, including squamous cell carcinoma, were diagnosed. Thirty of the 56 included samples were classified as International Federation of Gynecology and Obstetrics (FIGO) stage I, seven as FIGO stage II, 18 as FIGO stage III, and one as FIGO stage IV. The 5-year progression-free survival and overall survival rates were significantly higher for stage I disease than for stage II–IV disease (p < 0.001). In the multivariable analysis, surgery with residual tumor margins was a prognostic factor for progression, and FIGO stages I–IV and the absence of adjuvant therapy were prognostic factors for death. Conclusion : Surgery without residual tumor margins followed by adjuvant therapy may be a promising treatment for advanced-stage MT-MCTs.