Painting with broader strokes.
Top Line: Can elective nodal volumes be treated with pancreas SBRT?
The Study: Elective nodal volumes are typically covered with definitvie and adjuvant fractionated radiation for pancreatic cancer. But when using SBRT, narrow margins are often used that don’t typically include elective nodes--which is often criticized when comparing SBRT to ablative hypofractionated regimens. This retrospective, matched-cohort study from Stanford compares outcomes for definitive 5-fraction SBRT with (after 2018) or without (prior to 2018) elective nodal irradiation (ENI) in patients with unresectable pancreatic cancer. Gross disease plus a 3 mm margin was treated to 40 Gy in 5 fractions while elective nodal volumes received 25 Gy in 5 fractions. Nodal volumes were standard and included the porta hepatis, celiac, superior mesenteric, and peri-aortic nodes per the RTOG atlas. Stomach, duodenum, and bowel were limited to 40 Gy max, V33 < 1cc, and V30 < 5cc. There was no strict constraint on lower doses to bowel, however they aimed for a V25 < 30 cc. Compared to matched controls receiving SBRT alone, SBRT+ENI had a lower rate of local (20 vs 41%), regional (6 vs 22%), and combined locoregional progression (20 vs 51%). At 24 months, the cumulative rate of locoregional progression was 22.6% with ENI vs 44.6% without. In both groups, the most common site of nodal failure was in the peri-aortic region. While there was no major difference in grade 3+ toxicity, there was a significant increase in acute grade 1-2 nausea with ENI (60 vs 20%).
TBL: This retrospective study suggests that covering elective nodes with 25 Gy in 5 fractions as part of pancreas SBRT may reduce locoregional failure at the expense of increased low-grade GI toxicity. | Miller, Int J Radiat Oncol Biol Phys 2021