Pre-SBRT metabolic tumor volume and total lesion glycolysis to predict survival in patients with locally advanced pancreatic cancer receiving stereotactic body radiation therapy.

Abstract

189 Background: Though prior studies have demonstrated the prognostic value of pre- and post-treatment positron emission tomography (PET) parameters in other malignancies, the role of PET in pancreatic cancer is yet to be established. We analyzed the prognostic utility of PET for patients with locally advanced pancreatic cancer (LAPC) undergoing fractionated stereotactic body radiotherapy (SBRT). Methods: Thirty-two patients with LAPC received up to 3 doses of gemcitabine, followed by SBRT 6.6 Gy in 5 daily fractions, 33 Gy total, on a prospective clinical trial. All patients received a baseline PET scan prior to SBRT (pre-SBRT PET). Metabolic tumor volume (MTV), total lesion glycolysis (TLG), and maximum and peak standardized uptake values (SUVmax and SUVpeak) on pre-SBRT PET scans were calculated using an in-house software. Disease measurability was assessed at a threshold based on the liver standard uptake value (SUV) using the equation Livermean + (2 * Liversd). Median values of PET parameters were used as cutoffs when assessing their prognostic potential through univariate and multivariate Cox regression analyses. Results: Of the 32 patients in this study, the majority were male (N=19, 59%), 65 years or older (N=21, 66%), and had tumors located in the pancreatic head (N=27, 84%). Twenty-seven patients (85%) received induction gemcitabine prior to SBRT per protocol. Median overall survival for the entire cohort was 18.8 months (95% CI, 15.7-22.0). An MTV of 26.8 cm3 or greater (HR 4.46, 95% CI 1.64 to 5.88, p < 0.003) and TLG of 70.9 cm3 or greater (HR 3.08, 95% CI 1.18 to 8.02, p < 0.021) on pre-SBRT PET scan were associated with inferior overall survival on univariate analysis. Both pre-SBRT MTV (HR 5.13, 95% CI 1.19 to 22.21, p=0.029) and TLG (HR 3.34, 95% CI 1.07 to 10.48, p=0.038) remained independent prognostic factors for overall survival in separate multivariate analyses. Conclusions: Pre-SBRT MTV and TLG yield prognostic information on overall survival in patients with LAPC and may assist in tailoring therapy. Clinical trial information: NCT01146054.