Top Line: What is a safe and effective 3-fraction dose for pancreas SBRT?
The Study: The most frequently reported pancreas SBRT regimens typically use 5 fractions. This phase 1 dose escalation study sought to determine a safe 3-fraction dose for pancreas SBRT. It enrolled 24 patients with locally advanced disease (71% node positive) who received at least 3 months of systemic therapy (62.5% FOLFIRINOX). Dose was escalated from 24 Gy to 30 Gy and then 33 Gy. When it comes to pancreas SBRT, a point of debate is dose. The commonly used 33 Gy in 5 fractions regimen has a BED10 of ~54 Gy. Some argue this dose just isn’t enough to be more than a convenience compared to conventional radiation. So, the goal of this trial was to escalate dose to 33 Gy in 3 fractions with a BED10 of 69 Gy. This BED is close to the threshold of 70 Gy that has been associated with better outcomes. The target was the GTV plus a 5mm PTV margin using either respiratory gating or abdominal compression. Small bowel (excluding the duodenum) was limited to a max dose of 23 Gy, V20 of 5cc, and V10 of 16cc. The duodenum was limited to a V20 <10cc and a V15 <20cc. GI constraints took precedence over PTV coverage. No dose limiting toxicity was observed at any dose level, and there were no acute grade 3+ events. At 2 years, the rate of local failure was 31.7% and the rate of distant metastasis was 70.2%.
TBL: This small trial found that 33 Gy in 3 fractions resulted in no severe, grade 3+ dose limiting GI toxicity for locally advanced pancreatic cancer when prioritizing OAR dose constraints. | Reyngold, Int J Radiat Oncol Biol Phys 2023
The Study: The most frequently reported pancreas SBRT regimens typically use 5 fractions. This phase 1 dose escalation study sought to determine a safe 3-fraction dose for pancreas SBRT. It enrolled 24 patients with locally advanced disease (71% node positive) who received at least 3 months of systemic therapy (62.5% FOLFIRINOX). Dose was escalated from 24 Gy to 30 Gy and then 33 Gy. When it comes to pancreas SBRT, a point of debate is dose. The commonly used 33 Gy in 5 fractions regimen has a BED10 of ~54 Gy. Some argue this dose just isn’t enough to be more than a convenience compared to conventional radiation. So, the goal of this trial was to escalate dose to 33 Gy in 3 fractions with a BED10 of 69 Gy. This BED is close to the threshold of 70 Gy that has been associated with better outcomes. The target was the GTV plus a 5mm PTV margin using either respiratory gating or abdominal compression. Small bowel (excluding the duodenum) was limited to a max dose of 23 Gy, V20 of 5cc, and V10 of 16cc. The duodenum was limited to a V20 <10cc and a V15 <20cc. GI constraints took precedence over PTV coverage. No dose limiting toxicity was observed at any dose level, and there were no acute grade 3+ events. At 2 years, the rate of local failure was 31.7% and the rate of distant metastasis was 70.2%.
TBL: This small trial found that 33 Gy in 3 fractions resulted in no severe, grade 3+ dose limiting GI toxicity for locally advanced pancreatic cancer when prioritizing OAR dose constraints. | Reyngold, Int J Radiat Oncol Biol Phys 2023