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Pain response to palliative intent conventional radiotherapy for painful malignant iliopsoas involvement: a
Kenji Makita1,2, Yojiro Ishikawa3, Yuki Wada4
1Department of Radiation Oncology, National Cancer Center Hospital East, 6-5-1, Kashiwanoha, Kashiwa, Chiba, 277-8577, Japan. kemaki3@east.ncc.go.jp.
Background:
Evidence regarding the efficacy of palliative-intent conventional radiotherapy (conv-pRT) for painful malignant iliopsoas involvement (PMII), including malignant psoas syndrome (MPS)-related pain, caused by non-bone metastatic lesions remains limited to small, single-center studies. Therefore, we conducted the first multicenter study to evaluate the clinical effectiveness of conv-pRT for PMII/MPS.
Methods:
We retrospectively analyzed patients with PMII/MPS treated with conv-pRT between January 2013 and May 2025. Eligible patients received 8 Gy in 1 fraction, 20 Gy in 5 fractions, or 30 Gy in 10 fractions and had pain assessment available at ≥ 4 weeks after treatment initiation. Pain response was evaluated based on changes in pain scores and opioid consumption. Assessments were performed at 7 ± 3, 14 ± 3, 28 ± 7, and 56 ± 14 days from the start of conv-pRT. The best overall response (OR) during follow-up was determined.
Results:
A total of 54 patients were included. The median follow-up duration was 115 days (interquartile range, 62-186 days), and the 56-day survival rate was 86.8%. The best OR rate was 61%, including complete response in 24% and partial response in 37%, while 39% were classified as non-responders. Among responders, 91% achieved OR within 4 weeks. The best OR rate was not significantly associated with tumor burden parameters, including axial maximum diameter and clinical target volume, baseline Numerical Rating Scale score, baseline oral morphine equivalent dose, or the conv-pRT schedule.
Conclusion:
Conv-pRT provided clinically meaningful pain relief in approximately half of patients with PMII/MPS and may represent an effective palliative treatment option.
