Purpose: To test intensive alkylator-based therapy in desmoplastic small round-cell tumor (DSRCT).
Patients and methods: Patients received the P6 protocol, which has seven courses of chemotherapy. Courses 1, 2, 3, and 6 included cyclophosphamide 4,200 mg/m2, doxorubicin 75 mg/m2, and vincristine (HD-CAV). Courses 4, 5, and 7 consisted of ifosfamide 9 g/m2 and etoposide 500 mg/m2 for previously untreated patients, or ifosfamide 12 g/m2 and etoposide 1,000 mg/m2 for previously treated patients. Courses started after neutrophil counts reached 500/microL and platelet counts reached 100,000/microL. Tumor resection was attempted. Post-P6 treatment options included radiotherapy and a myeloablative regimen of thiotepa (900 mg/m2) plus carboplatin (1,500 mg/m2), with stem-cell rescue.
Results: Ten previously untreated and two previously treated patients have completed therapy. The male-to-female ratio was 11:1. Ages were 7 to 22 years (median, 14). The largest masses were infradiaphragmatic (n = 11) or intrathoracic (n = 1). Other findings included serosal implants (n = 11), regional lymph node invasion (n = 8), ascites or pleural effusion (n = 7), and metastases to liver (n = 5), lungs (n = 4), distant lymph nodes (n = 3), spleen (n = 2), and skeleton (n = 2). Tumors uniformly responded to HD-CAV, but there were no complete pathologic responses. One patient died at 1 month from tumor-related Budd-Chiari syndrome. Of seven patients who achieved a complete remission (CR), five remain in CR 9, 12, 13, 33, and 38 months from the start of P6, one patient died of infection at 12 months (autopsy-confirmed CR), and one patient relapsed 4 months off therapy. Of four patients who achieved a partial remission (PR), one remains progression-free at 34 months and three developed progressive disease. Five patients received local radiotherapy: three were not assessable for response, but in two patients, antitumor effect was evident. Four patients received thiotepa/carboplatin: two were in CR and remain so, and two patients had measurable disease that did not respond.
Conclusion: For control of DSRCT, our experience supports intensive use of HD-CAV, aggressive surgery to resect visible disease, radiotherapy to high-risk sites, and myeloablative chemotherapy with stem-cell rescue in selected cases.