Extragonadal germ cell tumors of the mediastinum and retroperitoneum: results from an international analysis.

PURPOSE: To characterize the clinical and biologic features of extragonadal germ cell tumor (EGCT) and to determine the overall outcome with currently available treatment strategies.

PATIENTS AND METHODS: Of an unselected population of 635 consecutive patients treated from 1975 through 1996 at 11 cancer centers, 341 patients (54%) had primary mediastinal EGCT, and 283 patients (45%) had retroperitoneal EGCT. Five hundred twenty-four patients (83%) had a nonseminomatous germ cell tumor (GCT), and 104 patients (16%) had a seminomatous histology.

RESULTS: After platinum-based induction chemotherapy with or without secondary surgery, 141 patients (49%) with mediastinal nonseminomas (median follow-up, 19 months; range, 1 to 178 months) and 144 patients (63%) with retroperitoneal nonseminoma (median follow-up, 29 months; range, 1 to 203 months) are alive (P =.0006). In contrast, the overall survival rate for patients with a seminomatous EGCT is 88%, with no difference between patients with mediastinal or retroperitoneal tumor location (median follow-up, 49 months; range, 4 to 193 months; respective 70 months; range, 1 to 211 months). A significantly lower progression-free survival rate was found in seminoma patients treated with initial radiotherapy alone compared with chemotherapy. Nonseminomatous histology, presence of nonpulmonary visceral metastases, primary mediastinal GCT location, and elevated beta-human chorionic gonadotropin were independent prognostic factors for shorter survival. Hematologic malignancies (n = 17) occurred without exception in patients with primary mediastinal nonseminoma. Sixteen patients developed a metachronous testicular cancer despite the use of platinum-based chemotherapy.

CONCLUSION: Whereas patients with pure seminomatous EGCT histology have a long-term chance of cure of almost 90% irrespective of the primary tumor site, 45% of patients with mediastinal nonseminomas are alive at 5 years. This outcome is clearly inferior compared with patients with nonseminomatous retroperitoneal primary tumors.