2. Department of Clinical Neurophysiology– Faculty of Medicine Cairo University, Al-Saray street, El-Manial, Cairo 11956, Egypt.
3. Department of Psychiatry - Faculty of Medicine Cairo University, Al-Saray street, El-Manial, Cairo 11956, Egypt.
4. Department of Biostatistics and Community Medicine- Faculty of Medicine Cairo University, Al-Saray street, El-Manial, Cairo 11956, Egypt.
Backgroud: To evaluate the doses of prophylactic cranial irradiation (1800cGy/1200cGy) as regards central nervous system (CNS) relapse, late cognitive abilities and learning disabilities.
Subjects and Methods: 42 patients treated for acute lymphoblastic leukemia (ALL) and categorized to be at high risk of relapse were assessed. None of the patients had CNS disease at diagnosis. 28 patients received 1800 cGy prophylactic cranial irradiation and 14 received 1200 cGy. All patients received intrathecal methotrexate as well as high dose methotrexate. Visual and auditory P300 studies were carried out after a mean of 4.6 years follow-up. Visual and auditory evoked potentials were done to assess visual and auditory functions at lower brain levels. Selected subscales of Wechsler Intelligence scale for children namely; similarities, vocabulary, picture completion, design, total performance, total verbal and total IQ and arithmetic abilities were applied to both subgroups.
Results: There was no difference in CNS relapse between the two groups (p=0.845). The 1800cGy group showed a significant delay of the visual P300 latency and reduction of the amplitude and delay of auditory P300 latency (p<0.001). In the 1200cGy group only the visual P300 was significantly abnormal (p< 0.001). Psychometric studies showed no significant differences between the 1800cGy /1200cGy subgroups in total IQ and arithmetic abilities. The 1800cGy subgroup showed significantly abnormalities in some subscales namely in similarities, total performance and picture.
Conclusions: Prophylactic whole brain irradiation if given for high risk ALL the recommended dose is 1200cGy due to the lower long term cognitive effect and no difference in the CNS relapse.
Keywords: Acute lymphoblastic leukemia, cranial radiation, late effects, relapse