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Association Between Previous Radiotherapy Response and Pain Response After Palliative Re-irradiation
Yutaro Koide1, Kenta Nimura1, Masamune Noguchi1
1Department of Radiation Oncology, Aichi Cancer Center, Chikusa-ku, Nagoya, Japan.
Purpose:
Pain response to palliative radiotherapy is often temporary; some require re-irradiation. Whether previous radiotherapy response is associated with response to re-irradiation within the same lesions remains unclear. This study compared pain response rates to palliative re-irradiation between patients with previous response and recurrent pain in the same lesion ("previous responders") and those with persistent or progressive pain after non-response to previous radiotherapy ("previous non-responders").
Methods And Materials:
This retrospective lesion-level analysis was conducted using a prospectively maintained observational cohort at a single cancer center. Patients receiving palliative radiotherapy for painful lesions were followed longitudinally from previous radiotherapy through re-irradiation or death. Between August 2021 and March 2025, 800 patients with 1,488 painful lesions 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 survival, 7.5 months). The re-irradiation cohort included 148 patients with 214 lesions; 63% were previous responders and 37% previous non-responders. The median interval from previous radiotherapy to re-irradiation was 6.1 months. At re-irradiation, 69% received single-fraction 8 Gy, the median NRS score was 7, and 77% were receiving opioids. Pain response after re-irradiation was observed in 93 lesions (43%). Response rates differed according to previous radiotherapy response: 60.0% among previous responders versus 15.2% among previous non-responders.
Conclusions:
Previous radiotherapy response was strongly associated with pain response after palliative re-irradiation, highlighting the heterogeneity within the previous non-responder population.