Significant risk factors for malignant transformation of ovarian endometrioma during dienogest treatment: a case report and retrospective study

BACKGROUND: To determine the prevalence of and risk factors for malignant transformation of ovarian endometrioma during dienogest therapy, which is very rare, we examined multiple cases of malignant transformation of ovarian endometrioma during dienogest therapy and performed a multivariate analysis of the records in our hospital. METHODS: The medical records of 174 patients who underwent DNGT for the treatment of OMA from June 1, 2011, to May 31, 2018, were reviewed retrospectively with the approval of the Human Ethical Committee of the University of Teikyo Hospital. And we provided one representative case of MT with obtaining written informed consent. To assess the effects of six representative factors, including advanced age, parity, surgical history, and endometrial cyst characteristics (including 3 factors), on the possibility of malignant transformation, we performed a multivariate logistic regression analysis. RESULTS: Of the 174 cases, 4 were diagnosed with malignant transformation, and these cases are reported. In the multivariate analysis, advanced age (P = 0.0064), nullipara (P = 0.0322), and enlargement (P = 0.0079) showed significant differences for malignant transformation occurrence. All 4 malignant transformation cases were among the 19 patients who had all of these 3 factors. CONCLUSIONS: For a more accurate determination of the treatment approach, a larger sample size will be needed to determine the risk factors for malignant transformation during dienogest therapy.