Metastatic Spine Tumors

In the United States there are about 1.2 million new cancer cases and about 550,000 deaths per year. Major cause of death is complication due to metastatic disease. Skeletal system is the third most common site of metastases after the lung and liver. The spine is the most common site of skeletal metastases [1, 2]. As many as 70% of cancer patients will have spinal metastases on autopsy studies. 10–30% of cancer patients will suffer from symptomatic spinal metastases [3].

The impact of spine metastases is ranging from pain, loss of mobility, bone fractures, and instabilities to paralysis due to spinal cord compression. The concepts for surgical treatment include decompression of neural elements, segmental fixation, and bone grafts. The main goals of surgical treatment in metastatic spine tumor are to restore/protect neurologic function, improve pain, and improve the quality of life [4]. The understanding of the spinal tumors biology is critical in defining the goals of treatment and determining the most appropriate therapeutic approach.

The Cancer Patient

The typical cancer patient is in 85% older than 55 years of age. The immune status is often compromised with decreased WBC (high risk of infections, lack of fever response), weight loss greater than 80%, increased catabolic state, decreased intake, low serum albumin less than 3–4 mg/dl, increased infection rate, decreased wound healing, chemo−/radiation/steroids, coagulopathy, thrombocytopenia, increased DVT, low platelet count, high rate of wound complications, increased age, altered immune system, cachexia, radiation/chemotherapy, and plastic surgery/flap closure. Therefore, patient evaluation is crucial for right decision-making. Before thinking about a surgical treatment, the medical fitness, the clinical presentation, the oncologic status, and the feasibility of surgical plan have to be taken into consideration in a multidisciplinary approach [5, 6].

Treatment Considerations

Regardless of the various therapeutic treatment options, a knowledge about the tumor entity is absolutely critical for an optimal treatment. In addition to the radiological diagnostic tools, a biopsy is often needed for correct diagnosis. Biopsies can be taken from a fine needle aspiration (FNA), a CT-guided core biopsy, or an open biopsy.

Preparative chemotherapy can be considered in patients with Ewing’s sarcoma, osteogenic sarcoma, high-grade chondrosarcoma, and dedifferentiated chordoma [7, 8].

Radiation before surgery can be reasonable in patients with a high risk of recurrence. However, Ghogawala et al. reported in their study an increased rate of major complications in patients with radiation before vs. de novo surgical decompression (32% vs.12%, p < 0.05) [9]. Planning/timing is very important to transfer the patient to the right treatment. Spine metastasis patients with “radio-resistant” tumors like melanoma, renal cell carcinoma, and sarcoma do not benefit from radiation, whereas myeloma and lymphoma present a high sensitivity for radiation.

Preoperative embolization is another treatment option which should be considered. Taking into account that 60% of all spinal metastasis are hypervascular, preoperative embolization “may help identify regional vascular supply of the spinal cord, decrease intraoperative blood loss, decrease local recurrence, and even provide palliative pain relief. Hypervascular lesions can be encased by the regional arterial supply making surgical excision extremely difficult and risky without embolization” [10].

Indications for Surgical Treatment

The current surgical treatment options range from limited decompression, invasive vertebroplasty/kyphoplasty to a radical en bloc resection with anterior and/or posterior stabilization and complex reconstructions techniques [11]. The most common goal of surgical treatment in metastatic spine is pain relief. Furthermore, a gross excision or en bloc resection may improve patients’ survival. Instability of vertebral metastases is an important indication for surgical treatment. The SINS score (spinal instability neoplasia score) is a comprehensive classification system for neoplastic instability in order to support the decision-making process for patients with spine tumors [12]. Risk factors for collapse in lumbar spine are pedicle destruction the percentage of involved vertebral body. The criteria for an impending collapse are fulfilled in cases of 35–40% body involvement alone or 25% body involvement with pedicle or posterior element destruction. Risk factors in thoracic spine are costovertebral joint destruction and the percentage of involved vertebral body. The criteria for an impending collapse are fulfilled in cases of 50–60% body involvement alone or 25–30% body involvement with costovertebral involvement [13]. Neurologic symptoms are important criteria for surgery including cord compression/myelopathy, nerve root compression/radiculopathy, and intractable pain.

The management options range from intra-lesional or en bloc resections, adjuvant chemo- or/and radiation-therapy to minimally invasive vertebroplasty/kyphoplasty. Indications for minimally invasive surgery include axial spine pain due to pathologic compression fractures and cases of multiple myeloma where bone quality limits surgical options, combined with radiosurgery as a primary treatment for painful metastatic vertebral collapse.

Surgical Considerations/Operation Planning

The surgery should be performed before radiation (if possible), before pathologic fractures occur, and while the patient is still neurologically intact. The technical feasibility, adequate approach, and exposure should be planned carefully before surgery. Most cases of metastatic spine tumors require a rigid posterior segmental instrumentation. Nevertheless, the surgical strategy for en bloc resection and stabilization should be defined, and if necessary, options for a soft tissue coverage should be discussed with plastic surgery.