Secondary Metastatic Tumors of the Spine

Overview

The American Cancer Society estimated that in 2011 alone, about 1.6 million new cases of cancer would be diagnosed, and about one third of that number are expected to die from cancer that same year. Metastatic disease is identified in about 70% of patients at the time of death, and metastasis to the spine is the most common osseous location (50% to 75%). Of those, 5% to 10% will have symptomatic spinal metastases. The most common primary cancers are breast, prostate, and lung, and of those, 16.5%, 15.6%, and 9.2%, respectively, are found to have symptomatic spinal metastases. A majority of the spinal metastases are located in the thoracic and lumbar regions (90%). Primary tumors may metastasize via direct extension or invasion, seeding into the cerebrospinal fluid, or hematogenously disseminating through the arterial, venous, or Betson’s plexus.

Clinical Presentation

The most common initial symptom is pain, which may be biologic and/or mechanical. Biologic pain is tumor-related and is characteristically a dull, constant ache with nocturnal exacerbation as a result of venous engorgement; a change in position or activity does not generally affect the pain intensity. Mechanical pain originates from structural abnormality in the spine with resultant increase in pain with motion. Standing, coughing, or any activity leads to increased pain. Frequently, patients are able to point to the spinal level involved during the evaluation.

Neurologic symptoms manifest when neural compression is present. Depending on the extent of the disease, patients may present with radiculopathy and/or myelopathy (weakness, sensory deficits, autonomic dysfunction).

Evaluation

Complete evaluation should include a thorough patient history, clinical exam, and appropriate laboratory work. Different systems have been developed to categorize neurologic status: the Frankel grade, American Spinal Injury Association (ASIA) impairment scale, and Eastern Cooperative Oncology Group (ECOG) performance status grade. These scales allow for ease of communication among medical personnel, and they help clinicians follow the patient’s clinical status ( Table 65-1 ).

Table 65-1

Frankel Grading System, American Spinal Injury Association (ASIA) Impairment Scale, and Eastern Cooperative Oncology Group (ECOG) Performance Score System

Grade	Description
FRANKEL GRADE
A	No motor or sensory function
B	No motor function, sensory function preserved
C	Nonambulatory
D	Ambulatory with neurologic symptoms
E	Normal motor and sensory function
ASIA IMPAIRMENT SCALE
A	No motor or sensory function
B	No motor function, sensory function preserved BNL
C	Motor muscle grade <3 in majority of muscles BNL
D	Motor muscle grade 3 in majority of muscles BNL
E	Normal motor and sensory function
ECOG PERFORMANCE STATUS GRADE
0	Fully active
1	Restricted in physically strenuous activity
2	Ambulatory, self-care, bed-ridden <50% of the day
3	Limited self-care, bed-ridden >50% of the day
4	Completely disabled, no self-care
5	Dead

BNL, below the neurologic level.

Imaging studies should include radiographs with flexion and extension views, computed tomography (CT), and magnetic resonance imaging (MRI) of the spine. Plain radiographs provide evidence of bony destruction and alignment of the spinal column, and they also localize the lesion. Approximately 30% to 60% of the bone loss, however, occurs before it may be visible on plain radiographs. Flexion and extension views are helpful in detecting any abnormal motion that may be present. CT will further evaluate the integrity of the vertebrae and osseous extension of the lesion ( Fig. 65-1 ), and MRI will determine the soft tissue extension of the lesion and will show any neural compression ( Fig. 65-2 ). Additionally, positron emission tomography (PET) and technetium bone scans may help determine whether the lesion is neoplastic or nonneoplastic and will identify other areas of metastasis. When a vascular lesion is suspected, angiography may be used for better characterization of the lesion and for possible preoperative embolization. For patients with prior spinal instrumentation, or when MRI is contraindicated, CT myelogram is very useful to assess the degree of neural compression. When a biopsy is performed as part of the initial evaluation, and tumor control is a goal of the surgery, the tract should be excised at the surgical intervention.

Management

The management of secondary metastatic spinal tumors requires the participation of medical and radiation oncologists and a spine surgeon, radiologist, rehabilitation medicine specialist, and the patient and family members. Treatment options include chemotherapy, radiation therapy, surgery, or a combination of these treatments. Patchell and colleagues reported that direct decompressive surgery plus postoperative radiotherapy is better than radiotherapy alone for patients with metastatic disease with spinal cord compression. A total of 101 patients were randomized into two groups that either received surgery plus radiation or radiation alone. Those who received surgery and radiation not only regained their ability to ambulate (62% surgery plus radiation vs. 19% radiation alone, P = .01), they were also able to do so for longer periods of time (median, 122 days vs. 13 days; P = .03). Radiation therapy should not be started within 3 weeks after surgery to allow ample time for wound healing and to delay the adverse effect of radiation on fusion.

For most spinal metastatic disease, the goal is palliative care of pain relief, preservation of neurologic function, and mechanical stabilization. In patients with progressive neurologic deficits, neural elements should be decompressed as soon as possible. The patient’s life expectancy must be at least 3 to 6 months when considering more extensive surgical intervention.

Different scoring systems have been developed to assist with surgical decision making that take prognosis into account. These include the Harrington classification, Modified Bauer score, Tomita scoring system, modified Tokuhashi scoring system, Sioutos, Van der Linden score, and the “LMNOP” system. The Tokuhashi and Tomita scoring systems are most commonly used in our institution.

The Tokuhashi system is a preoperative prognostic scoring system divided into six prognostic factors: 1) general medical condition, 2) number of extraspinal osseous metastases, 3) number of vertebral metastases, 4) metastases to the major internal organs, 5) primary cancer site, and 6) neurologic deficits ( Table 65-2 ). For each factor, the score ranges from 0 to 2. The estimated life expectancy correlates to the score: for a total score of 0 to 8, life expectancy is less than 6 months; for a score of 9 to 11, it is 6 months or more; when it is 12 to 15, life expectancy is a year or more. Management of patients is recommended based on the scoring system: 0 to 8, conservative treatment (radiation therapy alone); 9 to 11, palliative surgery (decompression with or without instrumentation); and 12 to 15, excisional surgery with stabilization ( Fig. 65-3 and Fig. 65-4 ).

Table 65-2

Revised Tokuhashi Scoring System for Prognosis of Metastatic Spine Tumors

Characteristic	Score
GENERAL CONDITION (KARNOFSKY SCORE, PERFORMANCE STATUS)
Poor (10% to 40%)	0
Moderate (50% to 70%)	1
Good (80% to 100%)	2
NUMBER OF EXTRASPINAL BONE METASTASES FOCI (BONE SCAN)
≥3	0
1 to 2	1
0	2
NUMBER OF METASTASES IN THE VERTEBRAL BODY
≥3	0
1 to 2	1
0	2
METASTASES TO THE MAJOR INTERNAL ORGANS
Unremovable	0
Removable	1
No metastases	2
PRIMARY SITE OF CANCER
Lung, osteosarcoma, stomach, bladder, esophagus, pancreas	0
Liver, gallbladder, unidentified	1
Others	2
Kidney, uterus	3
Rectum	4
Thyroid, breast, prostate, carcinoid tumor	5
PALSY (FRANKEL GRADE)
Complete (A, B)	0
Incomplete (C, D)	1
None (E)	2