Malignant mediastinal germ cell tumors: an intergroup study

This review was conducted to determine clinical characteristics and response to therapy in this rare pediatric neoplasm.

An intergroup Pediatric Oncology Group (POG) 9049/Children's Cancer Study Group (CCG) 8882 randomized trial was conducted to evaluate response rate and survival with chemotherapy using etoposide, bleomycin, and high or standard dose cisplatin for high-risk malignant germ cell tumors at extragonadal sites. For this review, a secondary analysis of clinical and operative findings in patients with primary site in the mediastinum was carried out.

Of the 38 children with malignant mediastinal germ cell tumors (MGCT), 36 had sufficient data to be included in this review. Thirty-four tumors were anterior mediastinal, 2 were intrapericardial. Younger patients had respiratory complaints; older patients had chest pain, precocious puberty, or facial fullness. Yolk sac tumor was the only malignant element in girls. Boys had yolk sac tumor in 7, germinoma in 3, choriocarcinoma in 2, and mixed malignant elements in 15. Benign teratoma elements coexisted in 22 patients. Four patients had biopsy and chemotherapy without tumor resection, and only 1 survived. Fourteen patients had resection at diagnosis followed by chemotherapy with 12 survivors. Eighteen patients had biopsy followed by chemotherapy and postchemotherapy tumor resection with 13 survivors. Tumor size in response to chemotherapy for these 18 patients was stable or increased in 6, and decreased in 12 (mean decrease of 57% in greatest dimension). Overall, 26 of 36 patients survived, with a 4-year patient survival rate of 71%+/-10%, and a 4-year event-free survival rate of 69%+/-10%. Ten patients died: 5 of tumor (all boys > or =15 yr), 2 of sepsis, and 3 of second malignancy.

Malignant MGCT is a complex tumor of varied histology with frequent coexistence of benign elements. Lesions often have incomplete regression with chemotherapy alone. Tumor resection may be undertaken at diagnosis or after attempted shrinkage with chemotherapy. Aggressive attempt at complete tumor resection should be offered to all patients even if bulky tumor persists after induction chemotherapy with expectation of a significant salvage rate. Boys > or =15 years may be a high-risk subgroup for mortality from tumor progression.