Ori Barzilai, Mark H. Bilsky, and Ilya Laufer

Abstract

Therapy for metastatic tumor treatment serves a palliative function and must be directed toward improvement of the patient’s quality of life. The goals of spinal metastatic tumor treatment include restoration or preservation of neurological function and spinal column stability, pain relief, and local tumor control. NOMS provides an evidence-based decision framework for treatment plan development in patients with spinal metastases and consists of neurological, oncological, mechanical, and systemic considerations. Data demonstrating the ability of SRS to safely deliver ablative radiation doses and achieve durable local control has revolutionized the type and extent of surgical procedures currently utilized. Extensive, often morbid, surgeries aiming for complete tumor removal or cytoreduction are being replaced with less invasive surgical options such as separation surgery or minimally invasive procedures. Separation surgery is a posterolateral approach to circumferential spinal cord decompression and stabilization. Minimally invasive surgeries (MISs) are currently used often as they entail limited perioperative morbidity, allow for quick recovery, and have shown to lead to less blood loss, low transfusion rates, and short hospitalizations. Spinal instability neoplastic score facilitates diagnosis of spinal mechanical instability, with patients with instability requiring cement or instrumented stabilization. Familiarity with the surgical, radiation, and systemic therapy options allows tailoring of optimal treatment strategy.

Keywords: spine, tumor, MESCC, NOMS, separation surgery, radiosurgery, SRS

20.1 Introduction

The number of people requiring treatment for spinal metastatic tumors continues to increase due to increasing elderly population and improved survival of cancer patients. The goals of spinal metastatic tumor treatment include restoration or preservation of neurological function and spinal column stability, pain relief, and local tumor control. Therapy for metastatic tumor treatment serves a palliative function and must be directed toward improvement of the patient’s quality of life. Familiarity with the surgical-, radio-, and systemic therapy options allows selection of optimal treatment strategy. The current chapter focuses on the presentation, diagnosis and decision-making, and surgery for spinal metastases.

20.2 Diagnostic Evaluation

20.2.1 Back Pain

Metastatic tumors frequently present with pain. Biological and mechanical pain represent the two primary pain patterns. Biological pain generally increases in severity during the night or early morning, without a clear exacerbation by movement. While the etiology of this pain pattern required further research, the pain is likely due to tumor-associated inflammation and the diurnal variation of endogenous steroid production playing a likely role and lower steroid production during the night contributing to increased pain. This hypothesis is supported by the pain relief, generally achieved by administration of glucocorticoids. Pain relief after glucocorticoid administration generally serves as a good predictor of pain relief after radiotherapy. On the other hand, mechanical pain becomes more severe with movement and does not respond to steroid administration. Mechanical pain is generally attributable to vertebral fractures and requires surgical stabilization. In the thoracic spine, mechanical back pain is often elicited with recumbency or position change. Pain attributable to fractures in the thoracolumbar junction generally radiates to the lumbar spine. Gathering of back pain history may facilitate differentiation of biological and mechanical pain patters. During the physical examination patients should be observed while supine, sitting, standing, and ambulating and during position changes in order to make note of pain during movement that would be consistent with symptoms of mechanical instability.

20.2.2 Neurological Symptoms

20.2.3 Imaging

Back pain or neurological symptoms or radiculopathy or myelopathy in cancer patients should trigger urgent magnetic resonance (MR) imaging of the spine. While X-rays may serve as an initial screen for fractures, they lack the soft tissue definition required for diagnosis of spinal tumors. Imaging of the full spinal axis is generally recommended since patients frequently present with multifocal spinal metastases. MR imaging has excellent sensitivity and specificity for osseous metastases, epidural and paraspinal tumor extension, and evaluation of the degree of spinal cord compression. Computed tomography (CT) imaging provides additional information about the osseous structure and may be useful in evaluation of fractures. CT imaging of the chest, abdomen, and pelvis or whole-body positron emission tomography imaging are required to assess the systemic tumor burden, and play an important role in therapeutic decision making.

20.3 Treatment Strategies

20.3.1 NOMS

Treatment goals for patients with spine metastases are palliative and include preservation or restoration of neurological function, maintenance of spinal stability, palliation of pain, and durable local tumor control. There are several treatment options including surgery, systemic therapy, radiation therapy, or combinations of these modalities. Selecting the optimal treatment in this complicated population is challenging and recent technological advancement, particularly in the field of radiosurgery along with advancement in systemic therapy owed to new biological treatments, complicates decision-making. The NOMS framework, consisting of neurological, oncological, mechanical, and systemic considerations, facilitates clear patient description and treatment decisions. This framework incorporates evidence-based treatment recommendations and can also be adopted to incorporate new technology and therapies. The neurological and oncological considerations are used in concert in order to determine the optimal radiotherapy and to determine whether the patient requires surgical decompression. The mechanical consideration serves as an independent indication for intervention, since spinal instability represents a mechanical problem requiring mechanical repair, such as cement or instrumented stabilization. The systemic consideration looks at the patient’s survival prognosis, extent of metastatic tumor burden, and medical comorbidities in order to determine whether they can tolerate the proposed treatment plan.

Neurological

The neurological evaluation combines a clinical examination and radiological evaluation. Clinically, patients are assessed for myelopathy or functional radiculopathy. The radiological evaluation focuses on the degree of epidural spinal cord compression (ESCC). Generally, it is not expected to find myelopathy on physical examination without radiographic evidence of epidural cord compression. Thus, although myelopathy on physical examination is an important factor, most of the weight of decision making relies on the degree of ESCC.