A phase II multi-institutional study to evaluate gemcitabine and fractionated stereotactic body radiotherapy for unresectable, locally advanced pancreatic adenocarcinoma.

Abstract

4045 Background: Phase I/II studies with single-fraction (25 Gy) stereotactic body radiotherapy (SBRT) for pancreatic ductal adenocarcinoma (PDA) have shown local progression free survival (LPFS) rates of >90%, but are limited by late GI toxicity and minimal tumor response. We performed a phase II multi-center trial of gemcitabine (GEM) and fractionated SBRT to determine if a high rate of LPFS with reduced toxicity could be achieved. Methods: After multidisciplinary review, 32 pts with locally advanced PDA received GEM in sequence with SBRT (6.6 Gy in 5 consecutive daily fractions, 33 Gy total). LPFS, metastasis free survival (MFS), and overall survival (OS) were measured from date of tissue diagnosis. Objective tumor response (OTR) was assessed by RECIST/PERCIST. EORTC QLQ-C30/PAN26 questionnaires were used to measure QOL. Results: Median f-up was 12 mos (range, 2-23). Mean age was 69.9 yrs (SD, 9.8) and 62% were male. Pts received a mean of 2.2 (SD, 1.0) GEM doses prior to SBRT and 8.3 (SD, 5.6) doses total. All pts completed SBRT. Median OS was 15.9 months (95% CI, 12.7-18.8). Stratification by CA19-9 > or < 90 at diagnosis yielded a hazard ratio of 6.2 for > 90 (p=0.021). Median LPFS has not been reached and median MFS was 10.2 mos (95% CI, 2.9-17.5). LPFS rate at 1 year was 87%. OTR on CT was seen in 41%, while 41% had stable disease and 18% progressed. Tumor metabolic activity decreased in 17/18 patients with pre/post-SBRT PET available. Mean peak SUV was 4.0 pre-SBRT versus 2.4 post-SBRT (p=0.002). Median CA19-9 was reduced from 124.7 prior to SBRT to 43.9 afterwards. Acute toxicity included: grade 2 anorexia (37%), fatigue (28%), nausea (22%), abd pain (19%), weight loss (9%), diarrhea (3%); gr 3 nausea (9%); and gr 4 nausea (6%). Late gr ≥3 GI toxicity was seen in 9%. Mean QOL score 4 wks post-SBRT was similar to baseline (p=0.38). At 6 mos there was a trend towards improved QOL (p=0.07). Conclusions: Fractionated SBRT with GEM achieves high rates of LPFS and tumor response. Minimal grade ≥3 acute and late toxicity was observed. SBRT is more likely to benefit patients with Ca-19-9 <90. A combination of SBRT with more aggressive chemotherapy may further improve outcomes.