Spinal bone metastases in colorectal cancer: a retrospective analysis of stability, prognostic factors and survival after palliative radiotherapy

Background: This retrospective analysis aimed to analyse the stability of spinal bone metastases in colorectal cancer (CRC) patients following radiotherapy (RT) by use of a validated score and to assess prognostic factors for stability and survival. Methods: Ninety-four patients with osteolytic spinal bone metastases from CRC were treated at the Department of Radiation Oncology at the University Hospital Heidelberg between 2000 and 2014. The stability of each affected vertebral body was assessed according to the validated Taneichi bone stability score on the basis of the treatment planning CT scan prior to RT and also based on the follow-up CT examinations at 3 and 6 months after RT. Additionally, bone survival rates (time between first day of RT and death from any cause) as well as prognostic factors for bone survival were evaluated for all study patients. Results: Before RT, 59 patients (63%) were rated unstable according to the Taneichi score. Pathological fractures within the irradiated region were diagnosed in 43 patients (46%) prior to RT. New fractures or progression of previously collapsed vertebrae were diagnosed in 4 patients (4%) after irradiation. Significant re-calcification and stabilization of former unstable bone metastases was only observed in 3/59 patients (3%) and 5/59 patients (9%). The median bone survival was 4.2 months (range 0.5-67.3 months) and 6 months after RT 61% of the patients were dead. Karnofsky performance score (KPS) (< 70% vs. = 70%), chemotherapy and bisphosphonate therapy were predictive prognostic factors for bone survival. Conclusions: Our study population is characterized by poor bone survival and low re-calcification rates of unstable spinal bone lesions 3 and 6 months after RT. To avoid unnecessary hospitalisation and improve remaining QoL, short fractionated treatment schedules of RT may be prefered in this highly palliative situation, particularly for patients with a KPS < 70%.