MR imaging and single-photon emission CT findings after gene therapy for human glioblastoma

BACKGROUND AND PURPOSE: Our goal was to evaluate MR imaging findings after local intracerebral gene therapy in patients with glioblastoma and differen tiate postoperative contrast enhancement phenomena. METHODS: In all, 26 patients with supratentorial single lesion glioblastoma underwent tumor resection and intracerebral injection of murine retroviral vector-producer cells for gene therapy with the herpes simplex virus type I thymidine kinase gene/ganciclovir system. Serial contrast-enhanced MR stu dies were obtained before treatment and postoperatively on day I or 2; week s 2, 4, 9, 13, 17, 25, and 33; and every 8 weeks thereafter. Iodomethyltyro sine single-photon emission CT (IMT-SPECT) investigations also were perform ed in selected cases. RESULTS: Twelve patients showed nontumorous enhancement of various intensit ies after treatment, arising within 18 to 72 hours and persisting at 3 to 1 0 months. It was characterized by a strong local enhancement up to 20 mm th ick, which was initially nodular and later linear along the resection cavit y wall and surrounded by massive perifocal edema. This "flare" enhancement had features that clearly differed from those of residual tumor enhancement s and benign postsurgical enhancements. The IMT-SPECT investigations showed increased amino acid uptake in patients with enhancement from residual or relapsing tumor, but not in patients with flare. CONCLUSION: After local gene therapy, a unique dynamic, transient perifocal flare enhancement can occur on MR images. IMT-SPECT may help to differenti ate between tumorous and nontumorous flare enhancements in patients with en hancing tissue on MR images after gene therapy for glioblastoma.