332 - Dose Escalated Simultaneous Integrated Boost Versus Standard Palliative Radiotherapy for Bone Metastases: A Comparative Analysis

Purpose/Objective(s):

Palliative radiotherapy is effective for pain relief in bone metastases however the speed of response may be suboptimal with conventional dose schedules. Using Simultaneous integrated boost (SIB) technique it is possible to deliverer a selective escalated dose to gross tumor volume (GTV) within standard fractionation while respecting normal tissue constraints. We hypothesized that SIB-based palliative radiotherapy provides faster and superior early pain relief compared with conventional 30 Gy in 10 fractions, without increased toxicity.

Materials/Methods:

This is a prospective comparative observational single institute study evaluating 60 patients treated for symptomatic painful bone metastases between September 2021 and November 2025. Patients were allocated into three arms: Arm A—30 Gy in 10 fractions to planning target volume (PTV) (n=28); Arm B—30 Gy in 10 fractions to PTV with SIB to 35 Gy in 10 fractions to gross tumor volume (GTV) (n=21) and Arm C—30 Gy in 10 fractions to PTV with SIB to 33 Gy in 10 fractions to GTV (n=11). Patients were treated using Intensity Modulated Radiation Therapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT) with daily image guidance. Pain assessment was done using the Numerical Pain Rating Scale (NRS) at baseline, mid-treatment and one-week post-treatment completion. The Secondary endpoints of the study included assessment of analgesic use (WHO Analgesic ladder), treatment related toxicity (CTCAE v6.0), functional improvement, treatment interruptions and need for dose escalation. Statistical analysis was performed using one-way ANOVA and chi-square testing.

Results: Baseline pain scores at initiation of treatment were comparable across all 3 arms (mean NRS 8.0–8.4; p>0.05). Mid-treatment pain scores at 5 fractions of radiation showed a non-significant trend toward faster pain relief in both SIB arms (Arm B and Arm C). On assessment at one-week post-treatment the patients receiving SIB (Am B and Arm C) demonstrated significantly superior pain relief compared with conventional Arm (Arm A Vs Arm B: p=0.005; Arm A Vs Arm C: p=0.035). Mean pain scores at one-week post treatment (NRS scores) were 4.1 (Arm A), 2.7 (Arm B), and 3.0 (Arm C). No toxicities or treatment interruptions were observed across all 3 arms. Functional improvement was observed in all patients of Arm B and Arm C however 96.42% patients in Arm A experienced functional improvement.

Conclusion:

SIB-based palliative radiotherapy (33–35 Gy in 10 fractions) provides significantly faster and early pain relief as compared to conventional 30 Gy in 10 fractions. SIB can be used as a practical and resourceful strategy to optimize palliative radiotherapy for painful bone metastases. This pragmatic dose-escalation strategy may enhance palliative care efficiency, reduce retreatment, and form future clinical practice and prospective trials.