RESULTS OF REIRRADIATION OF PRIMARY INTRACRANIAL NEOPLASMS WITH 3-DIMENSIONAL CONFORMAL THERAPY

We evaluated the potential of three-dimensional conformal therapy for re-irradiation of selected intracranial neoplasms and reviewed the ret reatment of 20 patients at the University of Michigan between May 1988 and August 1991. All patients had previously undergone a full course of external beam radiotherapy (RT) to a median dose of 5,940 cGy (rang e 5,100-6,500 cGy), including five whole brain treatments. All recurre nces were unsuitable for brachytherapy or radiosurgery. Various histol ogies were retreated, including 14 high-grade gliomas. Median time to re-irradiation was 38 months (range 9 months to 19 years, 6 months). R T was delivered with complex plans designed using fully integrated com puted tomography/magnetic resonance imaging (CT/ MRI) tumor volume inf ormation, and regions of previous parenchymal treatment were avoided i f possible. Composite (initial + retreatment) dose-volume histograms ( DVH) of dose to nontarget brain allowed comparison of alternative plan s to select beam orientations which minimized normal brain irradiation . Mean target dose of re-irradiation was 3,600 cGy (range 3,060-5,940 cGy). Total cumulative dose ranged from 8,060 to 11,940 cGy. Median su rvival was 9 months, and 1-year actuarial survival was 26%. After retr eatment, 8 of 12 patients (67%) had steroid dose decrement and neurolo gic improvement at 4-48 months (median duration 14 months). Radiograph ic regression or stabilization of disease was noted in 11 of 16 patien ts (68%). Re-irradiation with highly conformal three-dimensional plann ing provides frequent clinical improvement with acceptable morbidity a nd should be considered in selected patients with recurrent intracrani al neoplasms.