Analysis of the Relation between Pretreatment ADC Value and Prognosis in Patients Treated With Concurrent Chemoradiation Therapy for Locally Advanced Pancreatic Cancer

Abstract

The purpose of this study is to investigate the predictive usefulness of the apparent diffusion coefficient (ADC) value in diffusion weighted magnetic resonance imaging before the concurrent chemoradiation (CCRT) for locally advanced pancreatic cancer (LAPC). We retrospectively analyzed 18 LAPC patients who underwent CCRT from February 2009 to December 2014 in our institution and had evaluable diffusion-weighted image. Radiotherapy was given with expiratory breath-hold intensity modulated radiation therapy (IMRT) to a dose of 36-51Gy (median: 43.5Gy) in 15 factions, and gemcitabine 1000mg/m2 was given concurrently. They were 9 males and 9 females, and median age was 65.5 years old (42-83 years old). Sixteen patients had Eastern Cooperative Oncology Group Performance Status (PS) of 0, and the others had PS of 1. Thirteen patients had T4 cancer (Stage III) according to the 7th Union for International Cancer Control staging system and one of them had regional lymph node metastasis, and the others had T3 cancer without metastasis (Stage IIA). The ADC of the tumor was calculated from 2 different b-value diffusion weighted images (0 or 500 and 1,000 s/mm2). The overall survival (OS), local recurrence-free survival (LRFS), and distant disease-free survival (DDFS) was evaluated by Kaplan-Meier analysis. The log-rank test and univariate Cox proportional hazards model was also used to evaluate the association between mean ADC value in whole gross tumor volume (mADCt) and OS, LRFS, and DDFS. With a median follow-up of 16.5 months (range: 10.3-47.0 months), the median survival time (MST), median LRFS, and median DDFS were 16.5 months, 11.6 months, and 10.3 months (range: 10.3-47.0 months, 3.9-47.0 months, and 1.2-34.0 months), respectively. The median mADCt value was 1.37 x10-3 mm2/s (range: 1.06-1.77 x10-3 mm2/s). The mADCt value less than the higher one-third (<1.44 x10-3 mm2/s) was significantly associated with OS (MST 13.8 vs 27.5 months, p=0.015) and LRFS (median 10.7 vs 21.1 months, p=0.005), but was not associated with DDFS (median 9.6 vs 14.3 months, p=0.156) in the log-rank test. In the Cox model, there were significant relation between mADCt and both OS (HR 4.40, 95% CI 1.21-16.0, p=0.024) and LRFS (HR 5.82, 95% CI 1.52-22.3, p=0.010), but mADCt has no significant relation to DDFS (HR 2.13, 95% CI 0.73-6.21, p=0.165), as well. The mADCt before treatment may be useful to predict the OS and LRFS of LAPC patients treated with CCRT.