Treatment and Clinical Outcomes of Patients with Teratoma with Somatic-Type Malignant Transformation: An International Collaboration

Purpose: We assessed prognostic factors, treatments and outcomes in patients with teratoma with malignant transformation, a rare occurrence among germ cell tumors. Materials and Methods: Data on patients diagnosed with teratoma with malignant transformation between June 1981 and August 2014 were collected across 5 referral centers. Chemotherapy was dichotomized as based on germ cell tumor or teratoma with malignant transformation. Cox analyses were done to evaluate prognostic factors of overall survival, the primary end point. Each factor was evaluated in a univariable model. Forward stepwise selection was used to construct an optimal model. Results: Among 320 patients the tumor primary site was gonadal in 287 (89.7%), retroperitoneal in 17 (5.3%) and mediastinal in 16 (5%). Teratoma with malignant transformation and germ cell tumor were diagnosed concurrently in 130 patients (40.6%). A total of 49 patients (16.8%) initially presented with clinical stage I. The remaining patients were at good (123 or 42.3%), intermediate (42 or 14.4%) and poor (77 or 26.5%) risk for metastasis according to IGCCCG (International Germ Cell Cancer Collaborative Group). First line chemotherapy was given for germ cell tumor in 159 patients (49.7%), chemotherapy for teratoma with malignant transformation was performed in 14 (4.4%) and only surgery was done in 147 (45.9%). Median followup was 25.1 months (IQR 5.4-63.8). Five-year overall survival was 83.4% (95% CI 61.3 to 93.5) in patients with clinical stage I and it was also worse than expected in those with metastasis. On multivariable analyses nonprimitive neuroectodermal tumor histology (overall p = 0.004), gonadal primary tumor (p = 0.005) and fewer prior chemotherapy regimens (p < 0.001) were independent predictors of better overall survival. Chemotherapy was not independently prognostic. Conclusions: Less heavily pretreated teratoma with malignant transformation with a gonadal primary tumor and nonprimitive neuroectodermal tumor histology appears to be associated with longer overall survival. Generally, teratoma with malignant transformation had a worse prognosis than germ cell tumor. Uncertainties persist regarding optimal chemotherapy.