TOMOGRAPHY, September 2015, Volume 1, Issue 1: 37-43
Diffusion MRI Characteristics After Concurrent Radiochemotherapy Predicts Progression-Free and Overall Survival in Newly Diagnosed Glioblastoma
Departments of 1Radiological Sciences, 2Biomedical Physics, 3Neurology, and 4Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine; 5Department of Bioengineering, Henry Samueli School of Engineering and Applied Science; and 6Neuro-Oncology Program, University of California, Los Angeles, Los Angeles, CA
The standard of care for newly diagnosed glioblastoma (GBM) is surgery first, radiotherapy (RT) with concurrent temozolomide (TMZ) second, and adjuvant TMZ last. We hypothesized patients with low diffusivity mea- sured using apparent diffusion coefficient (ADC) histogram analysis evaluated after RT + TMZ and before adjuvant TMZ would have a significantly shorter progression-free survival (PFS) and overall survival (OS). To test this hypothesis, we evaluated 120 patients with newly diagnosed GBM receiving RT + TMZ followed by adjuvant TMZ. Magnetic resonance imaging was performed after completing RT + TMZ and before initiating adjuvant TMZ. A double Gaussian mixed model was used to describe the ADC histograms within the enhancing tumor, where ADCL and ADCH were defined as the mean ADC value of the lower and higher Gaussian distribution, respectively. An ADCL value of 1.0 µm2/ms and ADCH value of 1.6 µm2/ms were used to stratify patients into high- and low-risk categories. Results suggested that patients with a low ADCL had a significantly shorter PFS (Cox hazard ratio = 0.12, P = .0006). OS was significantly shorter with low ADCL tumors, showing a median OS of 407 versus 644 days (Cox hazard ratio = 0.31, P = .047). ADCH did not predict PFS or OS when accounting for age and ADCL. In summary, after completing RT + TMZ, newly diagnosed glioblastoma patients with a low ADCL are likely to progress and die earlier than patients with a higher ADCL. ADC histogram analysis may be useful for patient-risk stratification after completing RT + TMZ.