Celiac plexus radiosurgery for pain management in advanced cancer: An international phase II trial, health-related quality of life (HRQOL) outcomes.

e16293 Background: Upper abdominal / lower back pain characterizes celiac plexus involvement from pancreatic and other cancers which may impair HRQOL; its satisfactory treatment is an unmet clinical need. We hypothesized that ablative radiation delivered to the celiac plexus would decrease pain and improve HRQOL. Methods: An international single arm Phase II study included patients with an average pain level ≥ 5/11 on the brief pain inventory (BPI), ECOG 0-2, and anatomical involvement of the celiac axis. The intervention was a single fraction of 25Gy delivered to the celiac plexus. The primary endpoint was ‘complete or partial (≥2 points) pain response’ based upon the BPI ‘average pain’ 11-point scale. Changes in Health-related QOL at 3 & 6 weeks compared to baseline were secondary endpoints as measured by FACT-Hep, > 8 point change being the minimal clinically important difference (MCID). Evaluable patients included eligible irradiated subjects, who had stable pain levels pre-treatment, and were alive 3 weeks’ post-treatment. The sample size was 90 evaluable patients, giving 90% power to show response rate ≥ 40%. Opioid usage was assessed using intravenous morphine equivalent dose. Sensitivity HRQOL analyses imputed worsened outcomes (-9 for total FACT-Hep) for missing data. Results: Between 2018 and 2022, 149 patients were enrolled, 90/125 who received treatment were evaluable. Median age was 65.5 years (range 28-88), 65% were female, 92% had pancreatic cancer, and 86% had metastatic disease. Median Zubrod PS was 1, median number of systemic treatment lines was 1 (range 0-5), and median baseline opioid use 31 mg/d. At 3 weeks, 48 (53.3%, 95% CI 42.5-63.9) had at least a partial pain, the BPI ‘average pain’ score decreased by a mean of 2.5 points at 3 weeks (86/90 reported) and 3.2 points at 6 weeks (67/90 reported), both p<0.001. Opioid usage decreased by 0.6 mg/d at 3 weeks (NS) and 16.9 mg/d at 6 weeks (p=0.005). The FACT-Hep total score increased by 7.8 points at 3 weeks (54/90 reported, NS diff. from 8) and 16.6 points at 6 weeks (45/90 reported, sig. > 8, p = 0.01), showing an improvement in patients’ HRQOL. Changes in FACT-Hep were especially noted in the Physical Well Being subscale. The Trial Outcome Index (sum of physical, functional & disease-specific concerns) increased markedly at 3 weeks (6.6 points, p=0.005) after treatment and even more after 6 weeks (14.5 points, p<0.). Sensitivity analyses demonstrated improvements in HRQOL at 3 and 6 weeks (1.1, 3.8), but these were less than MCID. Conclusions: Celiac plexus SBRT decreases pain and opioid use amongst patients with pancreatic cancer and other tumors invading the celiac axis. The treatment appears to improve HRQOL. Clinical trial information: NCT03323489 .