A Computed Tomography Imaging Feature of Pancreatic Cancer As a Predictive Biomarker for Escalated Dose Radiation Therapy International Journal of Radiation Oncology, Biology, Physics POSTER VIEWING ABSTRACT| VOLUME 96, ISSUE 2, SUPPLEMENT , E171-E172, OCTOBER 01, 2016
Date
10/01/2016Abstract
Purpose/Objective(s)
Pancreatic ductal adenocarcinoma (PDAC) exhibits considerable heterogeneity in its biological and physical characteristics. Differences in the biophysical properties between individual tumors likely contribute to the variable outcomes of patients and quantifying these properties may be useful as biomarkers. We have identified a computed tomography (CT) imaging feature of PDAC that stratifies patients into distinct biological, physical, and clinical outcomes. The feature characterizes the change in enhancement from normal pancreas to tumor (called delta) on the CT scan. High delta tumors are more conspicuous on CT with significantly lower stroma and more mesenchymal features compared to low delta tumors. Further, patients with high delta tumors have poorer pathological response to standard dose RT compared to those with low delta tumors. We previously reported that escalated dose RT results in improved overall survival (OS) for patients with locally advanced PDAC (LAPC). Here we investigate whether the delta score can predict benefit to escalated dose RT.
Materials/Methods
We reviewed 122 patient records (78 male, 44 female) with LAPC from 2005-2015. Fifty patients received escalated dose RT (60-73 Gy at 1.8 to 4.5 per fraction with intensity modulated RT) and 72 patients received standard dose (50.4 Gy at 1.8 per fraction with 3D conformal technique). All patients typically received 4-6 months of induction chemotherapy and none exhibited metastatic progression by the time of starting RT. Pre-therapy CT images were used for delta scoring. Survival times were measured from start of RT. Log-rank Kaplan-Meier and Cox proportional hazards models were used for survival analyses.
Results
The proportion of high delta tumors was similar in the escalated RT group (60%, n = 30) and standard RT group (67%, n = 48; P = 0.5655). High delta patients had a significantly lower median OS (12.8 months) compared to low delta patients (21.2 months respectively, P = 0.006). On univariate and multivariate analyses, the baseline delta score and RT dose were associated with OS and distant metastasis free survival (DMFS). Patients with high delta tumors treated with escalated dose RT had a better 2 yr OS (38%) and 2 yr DMFS (19.3%) compared to patients with high delta tumors treated with standard dose RT (9% and 0% respectively; P = 0.04 and P = 0.06, respectively). Conversely, patients with low delta tumors treated with escalated dose RT had a similar 2 yr OS (36.4%) and 2 yr DMFS (22.63%) compared to patients with low delta tumors treated with standard dose RT (39.8% and 30.9%; P = 0.90 and P = 0.73, respectively).
Conclusion
Patients with high delta PDAC appear to benefit from escalated dose RT in terms of OS and DMFS. Stratifying patients with PDAC based on delta scoring may help guide treatment selection in ongoing and future clinical trials.
Author List
S. Moningi A. Amer L.E. Colbert Y. Lee W.A. Hall B.A. Erickson G.R. Varadhachary P. Das C.M. Taniguchi J.B. Fleming M. Katz C.H. Crane E.J. KoayAuthor
William Adrian Hall MD Chair, Professor in the Radiation Oncology department at Medical College of WisconsinView Online
