Prediction of life expectancy in patients with spinal epidural metastasis

Background: The treatment of spinal epidural metastasis is multidisciplinary and usually involves a team of medical oncologists, radiologists, radiotherapists, and spinal surgeons. Life expectancy is one of the factors considered when deciding whether surgery is warranted. Because expert estimates of life expectancy are generally not reliable, a prediction model is needed. Here, we temporally validated a model that was previously validated geographically.

Methods: The records of 110 consecutive patients who were referred with a spinal epidural metastasis were collected prospectively from 2009 to 2013 in order to validate the model, which was published in 2011. The actual and estimated life expectancies were represented graphically, and calibration and discrimination were determined. The calibration slope, Harrell's c-index, D, and R2D were calculated. Hazard ratios in the derivation set of 2011 were compared with the validation set. Misspecification was determined using the joint test for β*.

Results: The calibration slope was 0.64 ± 0.15 (95% CI: 0.34-0.94), Harrell's c-index was 0.72, D was 1.08, and R2D was 0.22, indicating slightly worse discrimination in the derivation set. The joint test for β* = 0 was statistically significant and indicated misspecification; however, this misspecification was attributed entirely to the surgical group.

Conclusions: We validated a prediction model for surgical decision making, showing that the model's overall performance is good. Based on these results, this model will help clinicians to decide whether to offer surgery to patients with spinal epidural metastasis.