Delayed response to brain tumor chemotherapy.

Five cases of recurrent malignant gliomas are reported. They showed unequivocal and long-lasting improvement of the clinical status and brain scintigram after progressive clinical and scintigraphic deterioration occurred during the initial courses of chemotherapy. The differential diagnosis of tumor regrowth and this unusual delayed response are discussed. Swelling of dead tumor cells and a secondary inflammatory reaction could explain the initial clinical deterioration. The delayed response may be consistent with the slow removal of dead cells from the brain. This has been observed experimentally. Evaluation of the response of a malignant glioma to chemotherapy should be made by serial observations during a sufficiently long period of time.