Accelerated Radiotherapy for Complicated Bone Metastases: SHARON Bone Randomized Phase III Trial Shows Non-Inferiority Compared to Standard Palliative Fractionation (NCT03503682)

<b>Objective:</b> The SHARON (Short course RadiatiON therapy for palliative treatment) Bone trial is a phase III randomized non-inferiority multicentric study comparing symptom relief for complicated bone metastases (BMs) achieved through hypofractionated accelerated palliative radiotherapy (RT) to a standard RT regimen. <b>Methods</b>: Eligible participants were adults with ECOG PS ≤ 3 who were referred for palliative RT for painful BMs. Patients were assigned to receive either 30 Gy delivered in 10 daily fractions or 20 Gy in 4 fractions over two consecutive days. The primary outcome was pain relief one month post-treatment. Pain relief and adverse events were also evaluated at 2, 3, 6, and 12 months after RT. This trial was registered at clinicaltrials.gov (NCT03503682). <b>Results:</b> Between February 2018 and November 2021, 83 patients were enrolled (30 Gy: 41; 20 Gy: 42). In the standard RT group, five patients did not complete the prescribed RT, while none in the experimental arm discontinued treatment (<i>p</i> = 0.026). Due to early mortality, the primary endpoint was evaluable in 73 patients (35 and 38 in the standard and experimental arms, respectively). The rate of complete pain response at one month was 22.9% and 28.9% in the 30 Gy and 20 Gy arms, respectively (<i>p</i>: 0.571). The overall pain response rates, which included complete and partial responses, were 74.3% and 78.9% in the 30 Gy and 20 Gy arms, respectively (<i>p</i> = 0.638), when considering at least a 2-point reduction in the numerical rating scale. In both arms, 4.8% of patients experienced Grade >2 toxicity. <b>Conclusions</b>: Administering 20 Gy in four fractions twice a day is non-inferior to the standard 30 Gy delivered in 10 fractions for pain relief in the context of complicated BMs. Furthermore, this regimen demonstrated comparable safety in terms of acute toxicity, with a lower incidence of definitive interruptions of radiotherapy.