SPINAL: study protocol for a multicenter non-inferiority trial evaluating reduce vertebral irradiation volumes in palliative radiotherapy for spinal bone metastases on analgesic efficacy

BACKGROUND: Palliative analgesic radiotherapy is commonly used to alleviate pain in patients with bone metastases. Traditionally, this approach involved irradiating the vertebrae above and below the painful lesion. The 2D/3D radiotherapy technique, characterized by a physical penumbra that could extend up to 50% of the vertebral height, often resulted in underdosing of the target volume and potentially reduced analgesic effectiveness. However, the advent of CT and MRI imaging, along with image-guided radiation therapy, has largely replaced these practices by enabling precise delineation of target volumes. With modern radiotherapy equipment, the physical penumbra has become negligible, reducing the need for large treatment margins and minimizing irradiation of healthy tissues and associated side effects. The primary objective of this study is to assess the impact of reducing the irradiated volume in palliative treatment of metastatic bone disease on analgesic effectiveness at day 30. As a secondary objective, the study aims to evaluate the effectiveness of telemonitoring in identifying patients who may benefit from patient-reported outcomes (PROs) and require additional care, such as further analgesic radiotherapy. METHODS: This clinical trial is designed as a multicenter, randomized, prospective non-inferiority study with two parallel arms: a standard arm involving spinal irradiation including adjacent vertebrae, and an experimental arm involving spinal irradiation with sparing of adjacent vertebrae. CONCLUSIONS: If successful, this approach could lead to significant changes in current palliative radiotherapy practices by reducing the risk of treatment-related toxicity and improving patients’ quality of life.