Pre-treatment DWI as a predictor of overall survival in locally advanced pancreatic cancer treated with Cyberknife radiotherapy and sequential S-1 therapy

BACKGROUND To identify the value of the pre-treatment apparent diffusion coefficient (ADC) derived from diffusion weighted imaging (DWI) in predicting the overall survival (OS) for locally advanced pancreatic cancer (LAPC) treated with Cyberknife followed by sequential S-1 chemotherapy. METHODS Patients with UICC-T4 LAPC who underwent DWI scan (3.0 Tesla) using two b-values (0, 600 s/mm2) in our center between 2015 and 2017 were enrolled. Mean ADCs of the region of interest (ROI) drawn manually on DWI imaging were measured by two independent radiologists at an interval of 1 month. The association between prognostic factors and patient survival was determined using univariate and multivariate analyses. Cox proportional hazard model was used for identification of independent prognostic factors of OS. RESULTS A total of 41 patients (28 males and 13 females) were included, with a median age of 64 years, with 5 patients (3 males and 2 females) lost. The median OS was 11.7 months (range 2.8-23.3) among all 41 patients. The 1-year OS was 46% (95% CI 30%-62%). Univariate and multivariate analyses indicated that pre-treatment ADC value (HR 10.652, P = 0.0093), age (HR 0.952, P = 0.015), CA19-9 (HR 1.001, P = 0.0022) and administration of S-1 (HR 0.128, P = 0.0002) were independent predicting factors of OS. CONCLUSION The mean ADC value of the primary tumor on pre-treatment DWI imaging was an independent predictor of OS in patients with LAPC receiving Cyberknife followed by sequential S-1.