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Primary bone tumors of the spine are rare with an estimated incidence of 2.5–8.5 cases per 100,000 people per year. Primary vertebral tumors account for fewer than 5% of spinal tumors. The clinical behavior of these lesions depends mainly on the pathobiology of the tumor.
Chondrosarcomas and chordomas are the most commons malignant primary bone tumors involving the spine. Between 6.5% and 10% of chondrosarcomas involve the mobile spine and approximately 5% are located within the sacrum. In the MD Anderson series of 21 spinal chondrosarcomas, 48% were located in the thoracic spine, followed by 33% in the lumbar and 19% in the cervical spine. Within the vertebra, chondrosarcoma is predominantly located in the vertebral body. Sacral chondrosarcomas are typically located eccentrically in the upper portion of the sacrum and frequently involve the sacroiliac joints. Most chordomas involve the sacrum.
Surgery is usually the initial treatment of choice for these tumors. In the past two decades, surgery for spinal tumors has evolved from palliative procedures to planned en bloc resections. Oncologic principles initially proposed by Enneking et al. in the 1980s to treat tumors affecting long bones as well as advanced surgical and instrumentation techniques have been gradually incorporated into spinal tumor surgery, and many groups have reported good clinical and oncological results with the use of more aggressive en bloc spinal resections.
In this chapter, the authors discuss the rationale for the surgical treatment of spinal chordomas and chondrosarcomas, preoperative planning, current indications for en bloc resections, surgical techniques in different spinal segments, clinical and oncological results, and complications of this type of procedure.
The objectives of surgery for spinal chordomas and chondrosarcomas are to preserve or even improve neurological function, relieve pain, prevent local tumor recurrence, and improve disease-free and overall survival. Surgical options range from intralesional resection to wide, “tumor-free margins” en bloc resection with spinal reconstruction.
Accumulating evidence demonstrates that en bloc resection with free margins is the best therapeutic option for achieving long-term and recurrence-free survival in patients with primary spinal tumors, including chordomas and chondrosarcomas. For example, en bloc spinal resections with disease-free margins has been shown to provide excellent local tumor control, with recurrence rates as low as 3%–8%. In contrast, intralesional resection results in recurrence rates of up to 100%. The landmark study from Kaiser et al. demonstrated that contamination of the surgical wound by cell seeding is the main factor associated with tumor recurrence. In their series, the rate of local recurrence was almost two times higher after en bloc resections that violated the tumor capsule than that achieved after en bloc resection without violation of the tumor capsule, demonstrating the key role of preserving tumor integrity during en bloc resections of spinal lesions.
Correct diagnosis and staging are crucial to the management of a suspected primary bone tumor of the spine. Tissue for histological diagnosis should be obtained by percutaneous computed tomography (CT)–guided trocar biopsy, which minimizes the risk of contamination of normal tissues by tumor. The orientation of the biopsy tract should allow its incorporation in the specimen of the definitive operation. Open biopsies should be avoided.
Careful preoperative planning is essential for determining whether en bloc resection is indicated and feasible. Imaging studies including whole spine CT and magnetic resonance imaging are usually recommended. Invasion of nearby vital structures (such as the aorta or vena cava) and the presence of intradural tumor that may prevent an en bloc removal without risking spinal cord injury are factors favoring a less aggressive approach. Systemic staging with CT of the chest, abdomen, and pelvis; bone scan; and positron emission tomographic scan is also an integral part of proper preoperative staging.
Currently, two staging systems are used to classify spine tumors as a guide to treatment planning. The Enneking classification, introduced in 1980 for appendicular musculoskeletal tumors, defines surgical terminology, categorizes tumors based on grade and extent, and emphasizes both tumor-free resection margins and avoidance of tumor entry during resection. When the tumor is not entered, the resection may be considered a wide (when a margin of normal tissue around the tumor is preserved) or marginal (when the obtained margin is along the tumor pseudocapsule) resection. In spinal oncology, marginal resection is preferred to a wide margin resection achieved by dural entry. When entry into the tumor occurs, the resection is considered intralesional (curettage). Radical resection, which refers to en bloc removal of a tumor and the entire compartment of origin, is rarely achieved in the spine without unacceptable morbidity (e.g., hemicorporectomy for a distal sacral chordoma). The Enneking classification ranges from Stage 1 to Stage IIIB ( Table 24.1 ; Fig. 24.1 ). All malignant tumors should be treated with wide en bloc resection as the tumor pseudocapsule cannot be considered a safe margin. Patients with metastasis on presentation do not benefit from en bloc resections and should receive palliative surgery and adjuvant therapy.
Stage | Grade | Site |
---|---|---|
IA | Low G1 | Intracompartmental T1 |
IB | Low G1 | Extracompartmental T2 |
IIA | High G2 | Intracompartmental T1 |
IIB | High G2 | Extracompartmental T2 |
IIIA | Any grade with regional or distal metastases | Intracompartmental T1 |
IIIB | Any grade with regional or distal metastases | Extracompartmental T2 |
The Weinstein–Boriani–Biagini (WBB) classification enables staging of spinal tumors while recognizing the unique anatomic complexity of the spine, such as involvement of the spinal epidural space and adjacent vascular structures ( Fig. 24.3 ), with the goal of establishing the feasibility and preferred type of surgical resection. Ultimately, the goal of this classification is to recommend the best approach to achieve tumor-free surgical margins while sparing the spinal cord ( Fig. 24.2 ) . The Enneking and WBB classifications have been shown to display moderate interobserver reliability and near-perfect intraobserver reliability for tumor staging and treatment guidance. The Enneking classification has also been shown to successfully predict the risks of tumor recurrence and mortality in primary spinal tumors.
In summary, preoperative planning should consider the indications, goals, and feasibility of en bloc resection; more specifically, these tools should be employed to determine whether there is a surgical corridor through which the tumor can be delivered without compromising the surrounding vital structures. To remove a spinal tumor in en bloc fashion, the arch formed by the bone elements of the spinal column (vertebral body, pedicles, and lamina) must be broken widely enough to allow dissection around the spinal cord. Sites of bone cuts should be selected carefully to yield tumor-free margins. These cuts can be made either across both pedicles, completely freeing the posterior element complex, or across one pedicle and the contralateral lamina. Sometimes, in order to achieve such en bloc resection, sacrifice of nerve roots is necessary. In such cases, the expected neurological deficits should be carefully taken into account when evaluating the risks and benefits of such aggressive operations.
Contraindications to en bloc spondylectomy include the presence of distant metastases, uncontrolled systemic disease, and encasement of adjacent visceral or vascular structures that cannot be excised.
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