Lower Baseline Apparent Diffusion Coefficient Values are Associated with Worse Survival in Locally Advanced Pancreatic Cancer

Abstract

It is challenging to obtain adequate pathologic tissue to personalize therapy for locally advanced pancreatic cancer (LAPC) patients. Noninvasive diffusion MRI (dMRI) has the potential to characterize underlying tumor biology and treatment responsiveness. Our prior work found a strong, significant association between pretreatment apparent diffusion coefficient (ADC) values and pancreatic tumor cell destruction in patients with resectable pancreatic cancer undergoing preoperative chemoradiation (chemoRT). The goal of the current study was to prospectively investigate the relationship between dMRI characteristics and outcomes after chemoRT in LAPC patients. Locally advanced pancreatic cancer patients were prospectively enrolled onto an IRB-approved clinical trial, investigating dMRI characteristics before and during chemoRT. High quality dMRI images in the tumor plane were obtained and two radiation oncologists delineated each tumor on T1-weighted MRI and dMRI images. Baseline and mid-radiation (mid-RT) ADC values were compared with time to local failure (TTLF), time to distant failure (TTDF), progression free survival (PFS), and overall survival (OS). Pre- and post-radiation CA-19-9 lab values were also obtained and compared with clinical outcomes. Univariable Cox proportional hazard models were used for statistical analysis. A total of 23 dMRI scans were obtained in 9 patients (6 male, 3 female) who received gemcitabine-based chemoRT. For the overall cohort, the median age was 64 years (range 52-73), median PFS was 18 months, and median OS was 25.3 months from diagnosis. Baseline dMRIs were obtained a median of 25 days (range 1 – 35) prior to radiation. We found a significant association between lower baseline ADC values and all clinical outcomes. Lower mean baseline tumor ADC values were associated with lower OS, lower PFS, shorter TTLF, and shorter TTDF (see Table 1). In comparison, there were no significant relationships between CA-19-9 lab values or mid-RT ADC values with any clinical outcomes. Lower baseline tumor ADC values were found to significantly correlate with clinical outcomes including worse survival in LAPC patients. These findings are concordant with prior studies showing poor pathological responses in resectable pancreatic cancer patients with lower baseline ADC values. Further research is needed in a larger cohort of patients to study how this noninvasive biomarker may help with clinical decision-making and treatment planning.Abstract 3443; TableCox Proportional Hazards Model of Mean Pancreatic Tumor ADCTimepointEndpointHazard Ratio95% CIp-valueBaselineOS0.650.4 – 1.00.0496BaselinePFS0.540.3 – 0.90.01BaselineTTLF0.180.04 – 0.80.02BaselineTTDF0.540.3 – 0.90.03Mid-RTOS1.130.8 – 1.60.51Mid-RTPFS1.080.8 – 1.50.65Mid-RTTTLF00 – Inf0.99Mid-RTTTDF0.650.4 – 1.10.13 Open table in a new tab