Clinical characteristics with radiation encephalopathy after intensity-modulated radiotherapy in nasopharyngeal carcinoma patients: analysis of 42 cases

Abstract

Objective To explore the incidence, clinical characteristics, and prognosis of radiation encephalopathy (REP) in nasopharyngeal carcinoma (NPC) patients after intensity-modulated radiotherapy (IMRT). Methods 870 NPC patients confirmed pathologically and without distant metastasis received radical IMRT,570 of which received chemotherapy simultaneously,and followed up for 6 -104 months (with a median of 40 months),undergoing magnetic resonance imaging (MRI) once every 3 months within the first 3 years after treatment and then once every year.The clinical manifestations were observed.In 29 of these 42 patients diagnosed as with REP,the dose distributions of REP lesions were evaluated.Results 4.83％ of the NPC patients (42/870) were diagnosed as with REP.There were 39 cases with pure temporal lesion (bilateral in 6 cases),with a median latency period of 30 months (6 -56 months),2 cases with pure cerebral stem lesion both with a latency period of 14 months,and one case with lesions in temporal lobe and cerebral stem with the latency period of 18 months.REP was not observed in the stage T1-2 patients.The incidence rate of REP was 3.09％ for the stage T3 patients and 14.35％ for the stage T4 patients.Twenty-two patients underwent following-up MRI after initial diagnosis of REP.After medication or surgical treatment the conditions became better or stable in the most cases. Dosimetric analysis of 32 injured temporal lobes in 29 patients found that the maximal dose was in the contrastenhanced lesions in 27 injured temporal lobes and in edema regions in 5 injured temporal lobes.For each patient,the maximal dose in the normal temporal lobe was lower than that in the injured temporal lobe.In the same patient,the maximal dose,minimal dose,and mean dose of contrast-enhanced lesions were all higher than those in the edema region.Conclusions The incidence of REP after IMRT is high,especially in local advanced NPC patients. Active treatment stabilizes or improves the REP condition. REP is positively correlated with dose of irradiation to brain tissue. Key words: Nasopharyngeal carcinoma; Intensity-modulated radiotherapy; Radiation encephalopathy