Pulsed reduced dose-rate radiotherapy for previously irradiated tumors in the brain and spine

Patients with unresectable locoregional cancer recurrences have limited management options. Reirradiation increases the risk of toxicity, particularly when perilesional dose-volume constraints are exceeded. We present and discuss two cases of previously irradiated tumors in the central nervous system (CNS) that was reirradiated using the pulsed reduced dose-rate radiotherapy (PRDR) technique. A 58-year-old female with a history of metastatic small cell lung cancer to the brain status post multiple rounds of radiation and chemotherapy presented with increasing weakness in her right arm and leg. Magnetic resonance imaging (MRI) revealed a growly peripherally enhancing 1.2 cm mass in the left precentral gyrus that had previously received prophylactic cranial irradiation and stereotactic radiosurgery. The patient was re-irradiated with 35 Gy in 100 fractions over 3 weeks, using PRDR with improved motor function at 3-month follow-up. A 41-year-old male with recurrent glioblastoma of the thoracic spinal cord presented with worsening neurological symptoms, including inability to ambulate due to bilateral leg weakness, causing wheelchair use. MRI thoracic spine revealed a recurrent thoracic lesion 2.2 × 1 × 0.8 cm. In addition to chronic chemotherapy, the patient was retreated palliatively in the same area at 50 Gy in 250 fractions, over 6 weeks, using PRDR. The treated lesion was stable on follow-up imaging, and the patient was able to walk with the assistance of a walker. In our two cases, PRDR proved effective in the treatment of recurrent malignant CNS tumors that were previously irradiated. Prospective studies are needed to delineate the efficacy and toxicity of PRDR.