Single-Fraction Celiac Plexus Radiosurgery: A Preliminary Proof-of-Concept Phase 2 Clinical Trial

Abstract

Refractory epigastric/midback pain is associated with locally advanced abdominal malignancies, especially pancreatic cancer. The pain is caused by tumor infiltration of the celiac plexus, a nerve network attached to the abdominal aorta. Contemporary palliative approaches are often inadequate. We hypothesized that ablative radiation targeted to the celiac plexus would alleviate this pain. We performed a single-arm prospective clinical trial (ClinicalTrials.gov identifier: NCT02356406). Eligible and evaluable patients had celiac pain of at least 5 out of 10 on the Numerical Rating Scale, completed treatment per protocol, and had at least 1 posttreatment visit. The entire retroperitoneal celiac plexus was irradiated with a single 25-Gy fraction. The primary endpoint was change in the Numerical Rating Scale 3 weeks posttreatment. Toxic effects and pain interference (as measured with the Brief Pain Inventory) were secondary endpoints. For our study, 31 patients signed consent, and, of these, 18 patients were treated and evaluable. Median age was 68 years (range, 51-79); 89% of the patients had pancreatic cancer; the median Eastern Cooperative Oncology Group performance status was 1; and the median interval from initial diagnosis to treatment was 9 months (range, 1-36), and, in this interval, patients received a median of 1 systemic treatment line (range, 0-3). Acute toxicity was limited to grade 1 to 2. Three weeks after treatment, 16 patients (84%) reported decreased celiac pain, with median pain level falling from 6 out of 10 (interquartile range [IQR], 5.0-7.5) at baseline to 3 out of 10 (IQR, 1.0-4.3); six weeks after treatment, the Numerical Rating Scale number fell further to 2.8 out of 10 (IQR, 0-3.3; both P < .005 vs baseline), including 4 patients who reported complete eradication of their celiac pain. Total daily morphine milligram equivalents decreased from 59 pretreatment to 50 at 3 weeks, and from 50 to 45 at 6 weeks. Significant improvement was seen in pain-interference scores. Celiac plexus radiosurgery appears to alleviate cancer-related pain. An international multicenter phase 2 trial is currently accruing.