Radiation myelitis following allogeneic stem cell transplantation and consolidation radiotherapy for non-Hodgkin's lymphoma

Myelitis is a rare but well documented complication of therapeutic radiatio n exposure to the spinal cord and is characterized by delayed development o f paresthesias, sensory changes and, in severe cases, progressive paresis a nd paralysis. Although accepted radiation tolerance limits for the spinal c ord have successfully limited the incidence of this problem (45-50 Gy, in d aily 1.8-2 Gy fractions), aggressive systemic therapy may render patients m ore susceptible to radiation-related neurotoxicity. We describe the case of a 38-year-old man with refractory non-Hodgkin's lymphoma who underwent mat ched sibling peripheral blood stem cell transplant following a conditioning regimen of cyclophosphamide (60 mg/kg x 2) and total body irradiation (120 cGy x 11), This was followed by delivery of 30.6 Gy involved-field radiati on at 1.8 Gy/day to the mediastinum and left supraclavicular fossa for bulk y residual tumor. Although maximum cumulative radiation dose to the spinal cord was less than 45 Gy, the patient subsequently developed progressive lo wer extremity weakness and MRI abnormalities of the spinal cord limited to the radiation field. This represents the second report in the literature of this unexpected complication, prompting a need to reexamine current guidel ines for radiotherapy in the context of high-dose systemic treatment.