Anesthesia for Spine Cancer Surgery

Introduction

Spinal cancer is primarily a metastatic disease with >90% having originated from another source. ^, In addition, osseous spread is the third most common form of metastasis with 30%–70% of cancer patients encountering spinal metastasis. Many primary tumors affect persons of advanced age, with more than 60% of cancer patients being older than 65 years. Consequently, particular consideration for comorbidities, fitness for therapy, and patient preference are fundamental in guiding management plans to provide holistic care.

Surgery for Spinal Metastases

Indications include mechanical instability, neurologic compression, debilitating pain, and removal of local disease to enable the use of other modalities. Most patients have a life expectancy of <1–2 years, and a balance exists between the risks and benefits of surgery. It is generally accepted that surgery might be considered in a patient with a life expectancy >3 months, with goals to optimize quality of life. ^,

Staging and Scoring Systems

Various classification systems aid surgical decisions based on the stage of the disease. The Global Spine Tumor Study Group (GSTSG) recommends the use of the Tomita and Tokuhashi staging systems. The Tomita score incorporates the rate of growth of the primary tumor, the number of bone metastases, and the number of visceral metastases. The Tokuhashi score includes the general condition of the patient, the primary site of the cancer, and the presence of palsy and metastasis ( Table 20.1 ). The use of the Spinal Instability Neoplastic Score (SINS) aids clinical diagnosis of spinal instability associated with cancer ( Table 20.2 ). Mechanical instability is an indication for surgical intervention. There are six parameters, including location, pain, alignment, osteolysis, vertebral body collapse, and posterior element involvement. A score of 13–18 indicates the need for surgical stabilization. Additionally, the use of quality of life scores, such as the Euroquol EQ5D, is encouraged by the GSTSG. Scoring systems can aid management plans. If no encroachment of the canal is evident and the vertebral column is stable, surgical intervention is not required.

Hematologic Malignancies

For myeloma, plasmacytoma, and lymphoma, there is a shifting treatment paradigm away from surgery. For myeloma, the mainstay of treatment is systemic chemotherapy, bisphosphonates, and pain control. For spinal involvement, methods including bracing and cement augmentation, radiotherapy or surgery may be used. Patients can develop rapidly progressive, lytic lesions that can cause spinal instability; however, treatment with instrumented stabilization may fail due to poor bone quality and infection. Bracing can provide pain relief and manage fractures. A case report noted successful management of an unstable myelomatous vertebral fracture without neurologic deficit using a thoracolumbar sacral orthosis for 3 months. Thoracic and cervical fractures with and without deficits were also effectively managed conservatively in this report. Such approaches restore stability without the risks of surgery. Patients with multiple myeloma and back pain, or an early clinical spine deformity, must still be screened urgently for spinal lesions.

Most patients with solitary bone plasmacytoma (SBP) develop multiple myeloma. The spine is the main site of SBP, and radical radiotherapy is the treatment of choice. Multiple solitary plasmacytomas are treated with radiotherapy in the absence of systemic disease. However, patients with extensive disease or early relapse may benefit from systemic therapy +/– autologous stem cell transplantation. Surgical intervention is not recommended first-line.

Regarding lymphoma, the National Institute for Health and Care Excellence (NICE) recommends management strategies, including radiotherapy, immunotherapy, chemotherapy, immunochemotherapy, and stem cell transplantation, with no role for surgery. These malignancies should be managed nonoperatively, similar to plasmacytoma and multiple myeloma, with surgery reserved for cases resistant to nonoperative treatment and progressive neurologic compression.

Cement Augmentation, Kyphoplasty, Vertebroplasty

Cement augmentation using balloon kyphoplasty (BKP) and percutaneous vertebroplasty (PV) is useful in reducing pain and restoring strength. It is indicated for patients who are nonambulatory and unable to engage in physical therapy, and patients who cannot tolerate analgesia side effects. Benefits include shorter operative times and hospital stays, and reduced blood loss and postoperative pain. PV and BKP involve the injection of cement under fluoroscopic guidance. The cement stabilizes the fracture and preserves stability. Some rare complications include cement embolus and neurologic dysfunction. Leaking of cement into the intervertebral disc is less rare and can cause fractures of other vertebral bodies. In BKP, a similar approach is taken; however, a balloon is inflated first to restore the vertebral height. BKP reports a lower cement leakage rate. This is performed for osteoporotic fractures; however, it is also a therapeutic option in pathologic fractures. Patients require careful clinical assessment, magnetic resonance imaging (MRI), and computed tomography (CT) in combination with a SINS score. Cement augmentation may be used to decrease pain and enhance stability following a fracture or prophylactically, if a fracture is likely.

Stereotactic Radiosurgery and Intensity-Modulated Radiotherapy

Stereotactic radiosurgery (SRS) and intensity-modulated radiotherapy (IMRT) target radiation precisely to the cancer to reduce injury to normal tissue. They allow for noninvasive, specific, and efficacious treatment. SRS targets a treatment site with multiple radiation beams of equal intensity. IMRT allows for variation of the intensity of each beam. It may be used solitarily or as an adjunct to surgery reducing the need for large resections. Evidence for these modalities is sparse due to small case series and limited follow-up periods. It has been shown to be a safe intervention; however, it has not been compared with existing techniques. Currently it is used for patients with recurrent disease for whom surgery is not available and is only accessible in centers with the appropriate technology and expertise.