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

PURPOSE: Current data regarding prognostic factors for malignant tumors arising from mature cystic teratomas (MT-MCTs) and effective treatments are insufficient. This study aimed to identify risk factors for MT-MCTs of the ovary. METHODS: Tumor samples diagnosed as MT-MCTs were collected from 13 institutions that participated in the Kansai Clinical Oncology Group. Based on the clinicopathological features and prognoses of the tumors, risk factors for progression and death were statistically assessed using univariable and multivariable analyses. RESULTS: Among the 60 tumor samples collected, 56 were diagnosed as MT-MCTs. Four samples were excluded 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 were classified as FIGO stage II, 18 were classified as FIGO stage III, and one was classified as FIGO stage IV. The 5-year progression-free survival and overall survival probabilities for stage I disease were significantly higher than those for stages 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 and adjuvant therapy may be promising treatments for advanced-stage MT-MCTs.