331 - Association Between Previous Radiotherapy Response and Pain Response After Palliative Re-Irradiation: Prospective Study

04:05pm - 04:15pm ET

Room 254

Presenter(s)

Yutaro Koide, MD, PhD - Aichi Cancer Center Hospital, Nagoya, Aichi

Y. Koide, K. Nimura, M. Noguchi, T. Kitagawa, T. Aoyama, S. Hashimoto, H. Tachibana, and T. Kodaira; Aichi Cancer Center, Nagoya, Japan

Purpose/Objective(s):

Pain response to palliative radiotherapy is often temporary; some require re-irradiation. Whether treatment responsiveness is preserved in the same painful lesions remains unclear. This study compared pain response rates to palliative re-irradiation between patients with prior response and recurrent pain in the same lesion (“previous responders”) and those with persistent nonresponse and progressive pain (“previous non-responders”).

Materials/Methods:

This prospective observational cohort study was conducted at a single cancer center. Patients receiving palliative radiotherapy for painful tumors were followed longitudinally from previous radiotherapy through re-irradiation or death. Between August 2021 and March 2025, 800 patients with 1,488 painful tumors were screened for eligibility. After excluding intracranial and postoperative lesions and limiting the analysis to lesions with an NRS score =2, 672 eligible patients with 1,125 painful lesions were included. Pain was assessed at 2, 4, 12, 24, 36, and 52 weeks after each radiotherapy course using standardized criteria. Data were censored on September 30, 2025. The primary outcome was pain response within 12 weeks after re-irradiation, based on the International Consensus Pain Response Endpoints. Secondary outcomes included overall survival and the interval between previous radiotherapy and re-irradiation.

Results:

By the data cutoff, 455 patients (68%) had died (median overall survival, 7.5 months). The re-irradiation cohort included 148 patients with 214 lesions; 37% were previous responders and 63% previous non-responders. The median interval from previous radiotherapy to re-irradiation was 12.7 months. At re-irradiation, 69% received single-fraction 8 Gy, the median NRS score was 7, and 77% were receiving opioids. Overall, pain response after re-irradiation was observed in 93 of 214 lesions (43%). Response rates differed markedly by previous radiotherapy response: 60.0% among previous responders versus 15.2% among previous non-responders.

Conclusion:

Differences in pain response to palliative re-irradiation between previous responders and non-responders indicate preservation of treatment responsiveness. These findings provide a practical basis for response-guided patient selection for re-irradiation.