Advanced pancreatic cancer: the use of the apparent diffusion coefficient to predict response to chemotherapy

The purpose of this study was to determine if the apparent diffusion coefficient (ADC) on diffusion-weighted MRI could predict the response of patients with advanced pancreatic cancer to chemotherapy. Diffusion-weighted MRI was performed in 63 consecutive patients with advanced pancreatic cancer who were subsequently treated with chemotherapy. The ADC values of the primary tumour with a middle b-value (400 s mm(-2)) and a high b-value (1000 s mm(-2)) were determined; cystic or necrotic components were avoided. The patients were classified into two groups: (i) those with progressive disease and (ii) those who were stable 3 months and 6 months after initial treatment. The groups were compared with respect to the ADC and clinical factors, including gender, age, Union International Contre le Cancer (UICC) stage, initial tumour size and chemotherapy agents used. Local tumour progression rates were evaluated using the Kaplan-Meier method. The middle b-value ADC of the pancreatic cancers ranged from 0.93-2.42 x 10(-3) mm(2) s(-1) (mean, 1.50 x 10(-3) mm(2) s(-1)) and the hi h b-value ADC ranged from 0.72-1.88 x 10(-3) mm(2) s(-1) (mean, 1.20 x 10(-3) mm(2) s(-1). The high b-value ADC was significantly different between the progressive and stable groups at 3 months' and 6 months' follow-up (p=0.03 and p=0.04, respectively). The rate of tumour progression was significantly higher in those with a lower high b-value ADC than in those with a higher b-value ADC (median progression time, 140 days vs 182 days; p=0.01). In conclusion, a lower high b-value ADC in patients with advanced pancreatic cancer may be predictive of early progression in chemotherapy-treated patients.