Preoperative embolization in surgical treatment of metastatic spinal cord compression

An increasing number of patients develop symptomatic spinal metastasis and increasing evidence supports the benefit of surgical decompression and spinal stabilization combined with radiation therapy. However, surgery for metastatic spinal disease is known to be associated with a risk of substantial intraoperative blood loss and perioperative allogenic blood transfusion. Anemia is known to increase morbidity and mortality in patients undergoing surgery, but studies also indicate that transfusion with allogenic red blood cells (RBC) may lead to worse outcomes. To reduce intraoperative bleeding preoperative embolization has been used in selected cases suspected for hypervascular spinal metastases, but no randomized trial has examined the effect. The final decision on whether preoperative embolization should be performed is based on the preoperative digital subtraction angiography (DSA) tumor blush, and as such considered the "gold standard" for determining the vascularity of spinal metastases. Reliability studies evaluating vascularity ratings of DSA tumor blush have not been published before. This PhD thesis is based on three studies with the following aims: I. To assess whether perioperative allogenic blood transfusions in patients undergoing surgical treatment for spinal metastases independently influence patient survival (Study 1). II. To assess whether preoperative transcatheter arterial embolization of spinal metastases reduces blood loss, the need for transfusion with allogenic RBC and surgery time in the surgical treatment of patients with symptomatic metastatic spinal cord compression (Study 2). III. To describe the vascularity of metastasis causing spinal cord compression (Study 2). IV. To evaluate inter- and intra-observer agreement in the assessment of the vascularity of spinal metastases using DSA tumor blush (Study 3). In conclusion the findings of this thesis demonstrate that preoperative embolization in patients with symptomatic spinal metastasis independent of primary tumor diagnosis does not reduce intraoperative blood loss and the need for allogenic RBC transfusion significantly, but does reduce the surgery time. However, a small reduction of intraoperative blood loss was observed in the hypervascular metastases. This tendency could be underestimated because of the study design and furthermore the tendency may be enhanced in metastases of only the most pronounced hypervascularity. The findings furthermore support that perioperative blood transfusion of less than 5 units does not decrease survival in patients operated for spinal metastases and transfusion of 1-2 units seems to be weakly associated with increased 12-month survival. It was demonstrated that approximately 75 percent of spinal metastases are hypervascular in a consecutive series of patients with symptoms of metastatic medullary compression and spinal instability operated by decompression and instrumented spinal stabilization. In addition the findings show that there is satisfactory moderate inter- and intrarater agreement in classifying the vascularity of spinal metastases on a three-step ordinal scale for DSA tumor blush. Nevertheless, there is a call for an accurate preoperative way to evaluate the vascularity of spinal metastases in order to select patients most likely to benefit from preoperative embolization.