Metabolic Tumor Volume (MTV) Is a Predictor of Survival in Borderline Pancreatic Cancers Treated With Neoadjuvant Therapy

Abstract

Purpose/Objective(s): A higher initial metabolic tumor burden is associated with lower median survival in locally advanced pancreatic cancer (LAPC), yet the prognostic utility of PET/CT is not defined in the setting of borderline resectable pancreatic cancer (BRPC). Materials/Methods: We performed a retrospective review of our institutional experience treating BRPC. Initial staging included endoscopic ultrasound as well as pancreas protocol CT and PET/CT scans. All patients underwent neoadjuvant gemcitabine-based chemotherapy and radiation therapy (RT). We limited the study to those patients receiving stereotactic body radiation therapy (SBRT) in 5 fractions. Restaging CT and PET/CT scans were obtained approximately 4 weeks following RT completion. The PET/CT scans were imported into a second program where the region of interest (ROI) was delineated over the pancreas primary tumor so that the MTV could be autocontoured. We measured the significance of the pretreatment and post-treatment SUV maximum and metabolic tumor volume (MTV) 2.5 to 5.0, which was defined as the MTVabove a threshold SUVof 2.5, 3.0, 4.0, and 5.0. Cox regression models were used to evaluate the significance between these parameters and disease free survival (DFS) and overall survival (OS). Results: We evaluated a total of 77 BRPC patients. Median follow-up was 9.2 months with a median dose of 35 Gy to the primary tumor/vessel interface. Sixty-two patients (80.5%) received induction chemotherapy with gemcitabine, docetaxel and capecitabine (GTX). Sixty-three (81.8%) underwent surgical resection. Significant predictors for OS included pretreatment MTV2.5 (p Z 0.017), mean SUV in pre-treatment MTV4.0 (p Z 0.034), mean SUV in pre-treatment MTV5.0 (p Z 0.021), post-treatment MTV3.0 (p Z 0.038), mean SUV in post-treatment MTV3.0 (p Z 0.034), post-treatment MTV4.0 (p Z 0.011), mean SUV in post-treatment MTV4.0 (p Z 0.009), post-treatment MTV5.0 (p Z 0.002), and mean SUV in posttreatment MTV5.0 (p Z 0.018). Differential SUV and MTV were not predictive. Conclusions: Our data suggests that preand post-neoadjuvant metabolic tumor volumes are prognostic for survival in BRPC. Author Disclosure: K. Latifi: None. A. Cruz: None. E. Mellon: None. T. Strom: None. J. Freilich: None. G. Springett: None. R. Kim: None. M. Malafa: None. R. Shridhar: None. S. Hoffe: None.