The Relationship Between Radiotherapy-Induced Pain Response Score and Pain Biomarkers TRPV1, β-Endorphin (bEP), Neurotensin (NT), and Orexin A (OXA) in Patients with Bone Metastases

<b>Objective:</b> Pain response scores were evaluated by associating pain biomarkers with several parameters affecting radiotherapy (RT)-induced pain response in patients with bone metastases. <b>Methods:</b> A newly developed 'revised pain and response scale' based on standardized scales was used for pain scoring. TRPV1, β-endorphin (bEP), neurotensin (NT), and orexin A (OXA) biomarkers were determined by ELISA before and after RT. <b>Results:</b> Pain response rates were 44.75% (<i>n</i> = 47) poor response, 10.5% (<i>n</i> = 11) moderate response, 44.75% (<i>n</i> = 47) good response. NLR before RT was higher in patients with poor response than those with good response (4.0 (1.3-36.7) vs. 2.6 (1.2-11.4), respectively (<i>p</i> = 0.036). NLR after RT was lower in patients with good response than in patients with poor response (3.1 (1.2-10.8) and 3.9 (0.8-37.2), respectively (<i>p</i> = 0.047). There was a significant correlation between response scores and NT, bEP, and TRPV1. In patients with good response, NT and bEP decreased, while TRPV1 increased, both of which were significant. Pre-RT and post-RT values were, respectively, NT: 631.4 (39.7-2863.0) vs. 400.3 (79.1-1479.0) <i>p</i> = 0.006) and bEP: 92.1 (18.7-228.8) vs. 49.1 (13.3-135.6) <i>p</i> ≤ 0.001). TRPV1 values: 321.7 (48.1-1100.7) vs. 352.8 (119.3-1510.9) <i>p</i> ≤ 0.001). <b>Conclusions:</b> The study found no difference in pain response scores between the different fractionation treatments. Significant changes in NT, bEP, and TRPV1 levels were seen in patients with a 'good response'. Pain response ratings were potentially least affected by OXA. Changes in NT, TRPV1, and bEP levels represent RT's pain response efficacy and patients' pain perception. These pain biomarkers may be included in guidelines as part of pain response monitoring strategies in the future.