Diabetes increases the risk of serious adverse events after re-irradiation of the spine.

Abstract

In this study we investigate the risk of radiation-induced serious adverse event of the spine in a large cohort of consecutive retreated patients with palliative radiotherapy (RT) for metastatic cancer in the spine. From 2010 to 2014, 2387 patients received spinal irradiation with a palliative intent for metastatic spinal cord compression at our institution. The patients were reviewed for prior RT and 220 patients had received re-irradiation of the spine. Clinical and treatment data were obtained from the patients' records and the RT planning system. Patients had metastatic disease from breast, prostate, lung, hematological or other cancers (22.7%, 21.8%, 21.4%, 3.2% and 30.9%, respectively). Median follow-up was 99 days. Median cumulative EQD2 was 57.6 Gy₂; range: 20.0-90.0 Gy. Spinal events related to re-irradiation were observed in fourteen patients; six patients were diagnosed with radiation-induced myelopathy (RIM) and nine patients with radiation-induced vertebral fracture (RIF). In a multivariate analysis, diabetes was related to increased risk of toxicity (HR = 7.9; P = 0.003). The incidence of RIM and RIF (6 and 9 out of 220 patients, respectively) was low in our cohort of re-irradiated patients. Patients with diabetes had a higher risk of adverse events which should be considered before re-irradiation of the spine.