Response of differentiated but not anaplastic teratoma to interferon.

A Phase 2 trial was conducted using intramuscular lymphoblastoid interferon (IFN, Wellcome Research Laboratories), 4 MU per day, in 10 patients with chemotherapy-resistant teratomas. There was stabilisation of disease in 2 patients both of whom were in retrospect considered to have had differentiated teratoma at the time of IFN administration. There was progression of presumed active anaplastic germ cell tumour in 8 patients. One of these patients, a 15-year-old boy with biopsy proven differentiated teratoma has received 2 courses of lymphoblastoid IFN and 1 course of recombinant leukocyte A IFN (Roche Products Ltd.) lasting 5 1/2, 8 and 8+ months respectively. He has had a mixed response in his differentiated tumour which on each occasion has been maintained for the duration that he received IFN. Rising HCG levels during his second course of interferon required additional cytotoxic chemotherapy. Lymphoblastoid IFN does not appear to be active against anaplastic germ cell tumours but both lymphoblastoid and recombinant leukocyte A IFN may be useful in the treatment of unresectable differentiated teratoma.