3569 - Radiation Therapy for Cancer Pain with and without a Neuropathic Component: A Single-Center Prospective Observational Study

Purpose/Objective(s):

In our previous exploratory study, we found that neuropathic pain in patients with cancer was associated with pain relief after radiation therapy. We aimed to validate this by comparing pain relief, pain interference with daily activities, and survival between patients with and without neuropathic pain.

Materials/Methods:

Patients who received palliative radiation therapy for painful tumors, including solid and hematologic malignancies, were enrolled at a single university hospital. Brief Pain Inventory data were acquired at baseline and at 1-, 2-, and 3-month follow-ups. At baseline, the treating radiation oncologist recorded whether the index pain (i.e., pain attributable to the irradiated tumor) had a neuropathic component according to the 2016 grading system established by the International Association for the Study of Pain. Opioid consumption was quantified using the daily oral morphine equivalent dose. The pain response in terms of the index pain was assessed using the International Consensus Pain Response Endpoints; responders were those with complete or partial responses.

Results:

Of 214 patients enrolled between 2017 and 2023, 96 (45%) had pain with a neuropathic component (definite, n =57; probable, n = 39). The median total radiation dose was 30 Gy (range, 8–66 Gy). At baseline, patients who had pain with a neuropathic component exhibited a higher intensity of index pain (P < 0.001), higher opioid dose (P = 0.028), higher Self-report Leeds Assessment of Neuropathic Symptoms and Signs score (P = 0.031), and greater mean pain interference score (averaged across 7 items) (P < 0.001) compared to patients without a neuropathic component. During the 3-month follow-up, a pain response was observed at least once in 56 of 96 patients (58%) with neuropathic pain and in 73 of 118 patients (62%) without neuropathic pain. A multivariable Fine-Gray model, treating death as a competing event, showed that the baseline presence of a neuropathic component did not predict a pain response (subdistribution hazard ratio, 0.93; 95% confidence interval, 0.64–1.34). For all evaluable patients at 2 months (n = 167), the mean pain interference scores were reduced from baseline (median, 4.9 vs. 2.0; P < 0.001). A multivariable linear regression model showed that the baseline presence of a neuropathic component did not predict changes in the mean pain interference score (beta coefficient, 0.60; 95% confidence interval, -0.15–1.35). Patients with and without neuropathic pain had comparable median overall survival (10.1 vs. 10.4 months; P = 0.59).

Conclusion:

Patients with painful tumors, regardless of whether the index pain had a neuropathic component, derived benefits from palliative radiation therapy. Ensuring access to palliative radiotherapy is crucial for patients with neuropathic pain that is often refractory to pharmacological therapy.