Retrograde Intrathecal Catheter Placement at L5/S1 for Sacropelvic Cancer Pain: A Pilot Feasibility Study

James S Cho,1,2 Julia Zhu,2 Pritesh Topiwala,1,2 David Hao1,2 1Department of Anesthesiology, Mass General Brigham, Boston, MA, USA; 2Harvard Medical School, Boston, MA, USACorrespondence: David Hao, Department of Anesthesiology, Mass General Brigham, 55 Fruit Street, GRB 444, Boston, MA, 02114, USA, Email david.hao@mgh.harvard.eduBackground: Intrathecal drug delivery systems have a role in treating cancer pain. For patients with predominant sacropelvic pain, caudally directed retrograde catheter placement targeting L5/S1 represents an alternative strategy that has been less well described.Objective: This pilot study evaluated outcomes associated with retrograde intrathecal catheter placement in patients with refractory sacropelvic cancer pain, with a primary focus on systemic opioid reduction and discharge facilitation.Methods: This pilot retrospective, pre-post cohort study was conducted at two academic medical centers between January 2021 and September 2024. Seven patients with cancer-related sacropelvic pain who received a caudally directed (retrograde) intrathecal catheter with tip positioning at L5/S1 were included. Pre-intervention data, including pain scores and daily oral plus intravenous opioid requirement, were collected and compared (two-tailed paired t-test) with post-intervention data. Patients were followed for up to six months.Results: Systemic (oral plus intravenous) opioid use decreased substantially from a pre-intervention mean of 731.8 ± 515.8 mg oral morphine equivalents (OME) in the 24 hours prior to intrathecal delivery system placement to 195.9 ± 93.4 mg in the 24 hours prior to discharge (t = 3.112, df = 6, p = 0.02), a mean reduction of 535.9 OME (95% CI: 114.46 to 957.25). Mean pain scores showed a modest reduction from 5.94 ± 1.64 to 4.55 ± 1.62, which, while statistically significant, should be interpreted cautiously given the small sample and absence of a comparator group. All five hospitalized patients were discharged within one week of implantation.Conclusion: In this small retrospective pilot cohort, retrograde L5/S1 intrathecal catheter placement was associated with substantial systemic opioid reduction and discharge facilitation. Findings are exploratory and hypothesis-generating; prospective comparative studies are needed.Keywords: cancer pain, intrathecal drug delivery, opioid reduction, pain management, palliative care