Posttreatment ADC changes in the periresectional area in patients with glioblastoma

BACKGROUND AND PURPOSE: Although targeted by radiotherapy, recurrence in glioblastoma occurs mainly periresectional due to tumour infiltration. An increase in ADC is shown posttreatment in the large high T2 area, however, until now ADC has not been investigated for the more relevant directly periresectional area. METHODS: Histogram analysis was used to assess periresectional ADC values in glioblastoma patients postradiotherapy versus preradiotherapy. Periresectional ADC values of 0-5 mm with 5 mm increment up to 20-25 mm were extracted and compared with a two-way repeated measurement ANOVA. RESULTS: Mean ADC values were significantly higher postradiotherapy directly adjacent to the resection area (0-5 mm) compared to preradiotherapy (p=0.017). The 0-5 mm ADC values were also higher than those in 5-10, 10-15 and 15-20 mm regions (p<0.05). Regional standard deviations of ADC values were higher postradiotherapy compared to preradiotherapy for the 0-5 up to 15-20 mm region, inclusive (p<0.05). Cox regression analysis however showed no survival benefits for the 0-5 mm area increase in ADC postradiotherapy. CONCLUSIONS: Increased ADC values representing a decrease in infiltrative tumour load was demonstrated in a limited direct periresectional area. This adds to previous studies looking at the larger high T2 area showing ADC response in relation to survival.