In a Belgian phase III trial (ROBOMET) reported in the Journal of Clinical Oncology, Mercier et al attempted to determine whether dose-escalated, single-fraction stereotactic body radiotherapy was associated with statistically significant benefit vs conventional, single-fraction, 3D conformal radiotherapy in the 1-month rate of complete pain response in patients with painful bone metastases.
Study Details
In the single-blind multicenter trial, 126 patients with up to three painful bone metastases were randomly assigned between April 2019 and October 2022 to receive a single stereotactic body radiotherapy fraction of 20 Gy (n = 63) or a single conventional radiotherapy fraction of 8 Gy (n = 63). The primary outcome measure was complete pain response at 1 month after radiotherapy in the intention-to-treat population.
Key Findings
After 1 month, complete pain response was observed in 23 of 63 patients (37%, 95% confidence interval [CI] = 25%–50%) in the stereotactic body radiotherapy group vs 16 of 63 patients (25%, 95% CI = 15%–38%) in the conventional radiotherapy group (P = .25). After 3 months, complete pain response was observed in 21 of 63 patients (33%, 95% CI = 22%–46%) in the stereotactic body radiotherapy group vs 15 of 63 patients (24%, 95% CI = 14%–36%) in the conventional radiotherapy group (P = .32). Among patients evaluable after 3 months and treated per protocol, 21 of 39 patients (54%, 95% CI = 37%–70%) in the stereotactic body radiotherapy group vs 15 of 48 patients (31%, 95% CI = 19%–46%) in the conventional radiotherapy group were complete responders (P = .048).
Grade 2 or 3 toxicity was observed in 15% of the stereotactic body radiotherapy group and 14% of the conventional radiotherapy group (P > .99). No grade ≥ 4 radiotherapy-related toxicity was observed. Fatigue was the most common grade 2 event in both groups. Grade 3 fracture in nonspine bone was observed in one patient in each group.
The investigators concluded: “[Stereotactic body radiotherapy] failed to demonstrate improved [complete pain response] rates after 1 month.”
Carole Mercier, MD, of the Department of Radiation Oncology, Iridium Network, Wilrijk (Antwerp), is the corresponding author of the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Flemish Stand Up To Cancer Foundation. For full disclosures of all study authors, visit the Journal of Clinical Oncology.
