Int J Radiat Oncol Biol Phys. 2021 Aug 1:S0360-3016(21)02600-6. doi: 10.1016/j.ijrobp.2021.07.1698. Online ahead of print.
ABSTRACT
PURPOSE/OBJECTIVES: Pancreatic stereotactic body radiation therapy (SBRT) is limited to gross tumor without elective coverage for subclinical disease. Given a better understanding of recurrence patterns, we hypothesized that the addition of elective nodal irradiation (ENI) to pancreatic SBRT would be tolerable and would decrease locoregional progression.
MATERIALS/METHODS: We conducted a retrospective 1:2 propensity-matched cohort study to compare toxicity and locoregional progression among patients treated with pancreatic SBRT with or without ENI. In the SBRT+ENI cohort, an elective target volume was delineated per RTOG guidelines and treated to 25 Gy in 5 fractions alongside 40 Gy in 5 fractions to gross disease. The primary outcome was the cumulative incidence of locoregional progression, with death as a competing risk.
RESULTS: Among 135 candidate controls treated with SBRT alone, 100 were propensity-matched to 50 patients treated with SBRT+ENI. All patients completed SBRT. Median potential radiographic follow-up was 28 months. The incidence of late and serious acute toxicity were similar between matched cohorts. However, SBRT+ENI was associated with a statistically significant increase in acute grade 1-2 nausea (60% vs. 20%, p<0.001). The 24-month cumulative incidences of locoregional progression with and without ENI were 22.6% (95% confidence interval [CI]: 10.0-35.1%) vs. 44.6% (95% CI: 34.8-54.4%, multivariable-adjusted hazard ratio 0.39, 95% CI 0.18-0.87, p=0.021). This was stable in sensitivity analyses of uniform prescription dose, multiagent chemotherapy, and resectability. There were fewer peripancreatic (0% vs. 7%), porta hepatis (2% vs. 7%), and peri-aortic/aortocaval (5% vs. 12%) recurrences after SBRT+ENI, but no difference in survival.
CONCLUSIONS: Pancreatic SBRT+ENI was tolerable and did not increase late or serious acute toxicity relative to a matched cohort undergoing SBRT alone, but did increase acute grade 1-2 nausea. The addition of ENI to SBRT was associated with decreased locoregional progression but not improved survival. Further studies are warranted to determine if ENI offers meaningful benefit.
PMID:34348171 | DOI:10.1016/j.ijrobp.2021.07.1698
