Malignant transformation of teratoma to primitive neuroectodermal tumor (PNET): Outcome analysis with PNET based chemotherapy

Abstract

e16121 Background: Metastatic testis cancer is uniquely chemosensitive and highly curable. Residual teratoma can be surgically resected. However, testicular teratoma can differentiate along endodermal, ectodermal, or mesodermal elements (malignant transformation of teratoma), with capacity to metastasize and not be amenable to surgical resection. We report results of malignant transformation of teratoma to metastatic PNET treated with PNET based chemotherapy. Methods: Retrospective review of 42 patients with PNET in testis or at metastatic sites seen at Indiana University from 1999–2007. Of these 42 patients, 10 had inoperable or unresectable PNET treated with cyclophosphamide 1200 mg/M2, doxorubicin 75 mg/M2, and vincristine 2 mg IV alternating with ifosfamide 1.8 grams/M2 × 5 days plus etoposide 100 mg/M2 × 5 days. Courses were given every 3 weeks for 6 courses or until progression or undue toxicity. Results: 9 of 10 patients had at least 1 prior platinum based combination chemotherapy regimen for their germ cell tumor. Tumor markers (human chorionic gonadotropin and alphafetoprotein) were normal at start of chemotherapy for biopsy proven PNET. Eight of 10 achieved objective response. Two of 10 are currently disease-free for 16 and 33 months from initiation of PNET specific chemotherapy and 3 other patients are alive with disease at 73, 34, and 30 months. These 5 patients all had subsequent surgery. Conclusions: PNET specific chemotherapy has a high objective response rate for malignant transformation of teratoma to PNET, with some patients capable of long-term survival with chemotherapy followed by surgical resection. [Table: see text]