The clinical data of 54 patients (57% males) with extracranial
primitive neuroectodermal tumors (
PNET) seen over a 20-year period at Memorial Sloan-Kettering
Cancer Center were reviewed. The age at diagnosis ranged from 1 month to 81 years (median, 17 years). One
PNET arose in a previously irradiated site. One patient had an unaffected identical twin. Primary sites were thoracopulmonary (n = 25), pelvis (n = 12), retroperitoneum or abdomen (n = 10), limbs (n = 5), neck (n = 1), and unknown (n = 1). At diagnosis, epidural extension was present in 13 patients with truncal primaries, and 11 patients had distant
metastases. All of the latter died with disease. Progression-free survival (PFS) among the 43 patients with localized
tumors (all greater than 5 cm) was 25% at 24 months. Two of 13 patients who relapsed after more than 12 months without
therapy were long-term survivors. Patients with localized
PNET who had resection of all gross disease within 3 months of diagnosis had a significantly longer PFS (P = 0.0003).
Radiation therapy caused
tumor shrinkage but was not curative of measurable disease. A dose-response effect was evident with the most commonly used
drug,
cyclophosphamide. Myeloablative regimens using
melphalan (n = 8) or
thiotepa (n = 1) with autologous bone marrow rescue were not clearly beneficial. The treatment results favor: (1) early surgical removal, (2) dose-intensive use of drugs active against
PNET (especially
cyclophosphamide), and (3)
radiation therapy to ablate residual microscopic disease.