Pain response to re-irradiation for non-bone metastatic lesions: a single-institution retrospective study.

Abstract

Background: Evidence regarding palliative re-irradiation (re-RT) for persistent or recurrent pain from non-bone metastatic lesions remains limited. This study evaluated pain response after re-RT in patients with persistent or recurrent painful non-bone metastases.

Methods: We retrospectively analyzed patients with persistent or recurrent painful non-bone metastases who underwent re-RT to the same previously irradiated lesion between January 2013 and October 2025 and had an evaluable pain assessment at 4 weeks, defined as 28 ± 7 days after re-RT initiation. Pain response was evaluated based on changes in pain scores and morphine dosage. Assessments were performed at 7 ± 3, 28 ± 7, 56 ± 7, and 84 ± 7 days after the initiation of re-RT, corresponding to approximately 1, 4, 8, and 12 weeks, respectively.

Results: Thirty-nine patients were included. The median follow-up was 128 days (interquartile range, 89-221 days). Re-RT regimens were 8 Gy in one fraction in 26 patients (67%), 20 Gy in five fractions in 12 (31%), and 30 Gy in 10 fractions in one (3%). The best overall pain response was observed in 26 patients (67%), including complete response in seven (18%) and partial response in 19 (49%). Among responders, 89% (23/26) achieved response within 4 weeks. The overall response rates were 25% (9/36) at 1 week, 51% (20/39) at 4 weeks, 63% (19/30) at 8 weeks, and 40% (10/25) at 12 weeks, respectively.

Conclusion: In this small retrospective cohort, approximately half of the patients achieved pain relief after palliative re-RT, and most observed responses occurred within 4 weeks. These preliminary findings warrant further evaluation in larger prospective studies using standardized pain and analgesic assessments.