20 Metastatic Disease of the Thoracic Spinal Column 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 Clinical Pearls • Back pain in cancer patients should trigger magnetic resonance imaging in order to determine the presence of spinal metastases. • NOMS provides evidence-based decision framework for treatment plan development in patients with spinal metastases and consists of neurological, oncological, mechanical, and systemic considerations. • Primary tumor histology determines the optimal radiotherapy selection, with radiosensitive tumors responding to conventionally fractionated radiotherapy and radioresistant tumors requiring stereotactic radiosurgery for durable control. • Patients with spinal cord compression due to solid tumor metastases require surgical decompression and stabilization followed by radiotherapy. • Spinal instability neoplastic score facilitates diagnosis of spinal mechanical instability, with patients with instability requiring cement- or instrumented stabilization. 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. 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. Neurological symptoms generally develop after the prodrome of back pain and may consist of radiculopathy due to nerve root compression or myelopathy due to compression of the spinal cord. Pain radiating into the arm, leg, or band-like thoracic pain may be indicative of nerve root compression caused by tumor. The development of neurological deficits attributable to compression of the spinal cord may have a variable time course and severity. Patients may experience ataxia or loss of proprioception, diminished sensation, paresthesia, weakness, and disturbances in bowel or bladder function. Radicular thoracic pain generally presents as unilateral or bilateral band-like pain radiating around the thorax and radiculopathy due to T1 tumors may radiate to the axilla or hand. Signs and symptoms of thoracic spinal cord compression may include diminished or altered sensation below the level of the tumor, ataxia and leg weakness, and bowel and bladder dysfunction. Neurological examination consists of proprioception, light touch and pin-prick sensation, muscle strength assessment, ambulation and testing for clonus, hyperreflexia, and Babinski’s sign. 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. 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. 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. The degree of ESCC is evaluated using a three-point scale originally developed by Bilsky et al and validated by the Spine Oncology Study Group (SOSG).1 The ESCC scale consists of six grades of compression: grade 0, grade 1A, grade 1B, grade 1C, grade 2, and grade 3. Grade 0 signifies bone-only disease; 1A, epidural impingement, without deformation of the thecal sac; 1B, deformation of the thecal sac, without spinal cord abutment; 1C, deformation of the thecal sac with spinal cord abutment, but without cord compression; 2, spinal cord compression, but with cerebrospinal fluid (CSF) visible around the cord; and 3, spinal cord compression, no CSF visible around the cord ( Fig. 20.1). The oncological evaluation accounts for the tumor histological type and responsiveness to available therapies. Modern anti-cancer treatments are revolutionizing cancer care and to date, these therapies include conformal external beam radio therapy (cEBRT), stereotactic radiosurgery (SRS), chemotherapy, hormones, immunotherapy, or biologics. Albeit the major advancements in cancer care, the mainstay of treatment for spinal metastasis remains radiation treatment. Historically, cERBT was adopted as the standard of care for patients with spinal metastases of all histologies.2 With surgical advancement and improved instrumentation, stronger evidence in support of combination surgical decompression combined with cEBRT became available.3,4,5 cEBRT delivers radiation through one to two beams to a treatment field that includes, but is not confined to, the tumor area. As there are organs at risk (OAR), particularly the spinal cord, within the radiation field, the dose of radiation is limited.6 Tumors are considered either radioresistant or radiosensitive depending on the response to cEBRT.7,8,9 Clinically, this results in the lower median response duration after cEBRT, repeatedly seen in radioresistant histologies in the literature.10,11,12 Lymphoma, seminoma, and myeloma are considered radiosensitive histologies along with solid tumors such as breast, prostate, ovarian, and neuroendocrine.10,13 Renal, thyroid, hepatocellular, colon, and non-small cell lung carcinomas, sarcoma, and melanoma represent radioresistant tumors.8,9,10,13 It is important to realize that regardless of the degree of ESCC, patients with radiosensitive tumors can be treated effectively with cEBRT.7,9
20.1 Introduction
20.2 Diagnostic Evaluation
20.2.1 Back Pain
20.2.2 Neurological Symptoms
20.2.3 Imaging
20.3 Treatment Strategies
20.3.1 NOMS
Neurological
Oncological