Author: Dr Ngian Kite Seng & Dr Tan Chong Tien & Dr James Tan
Date: October 2011 Issue
Welcome to our November issue of Spine Clinics. In this issue, we are sharing our experience with the most common spinal tumour – metastatic spinal secondaries. Management of this common condition is dictated by many factors. The main concern is the stability of the spine and the protection of the delicate spinal cord.
CASE STUDY
Madam B, a 72-year-old female, presented to my clinic recently with 3 months history of low back pain radiating to her left supra-iliac region. Her symptoms had worsened progressively. She had tenderness elicited by lumbar spine flexion. Neurological examination of her lower limbs was normal. X-ray and MRI of her spine revealed an extensive infiltrative lesion of T11 vertebral body, and its left pedicle. The posterior wall of the vertebra was eroded, and the lesion was encroaching onto the spinal cord and compressing it. The assessment was an extensive T11 spinal metastasis with cord compression and high risk of pathological fracture that could result in paralysis. Madam B underwent T11 decompression laminectomy with clearance of tumor tissue immediately surrounding the cord. The spine was instrumented from T8 to L1 segments to provide stability and to pre-empt pathological fracture. Frozen section of the specimen taken during surgery indicated the lesion to be lymphoma. This was later sub-typed as diffuse large B-cell lymphoma. Her back pain resolved completely following the surgery and she was ambulating well. She was referred to hematologist for outpatient chemotherapy treatment which started one week following the surgery.
DIAGNOSIS
There are potential pitfalls in the diagnosis of spinal metastasis. Spinal metastasis may not be suspected because it is a less common cause of back pain. Metastatic lesions may not be obvious on X-Ray until extensive bone destruction has taken place. Hence a strong index of suspicion is needed to pick up the diagnosis early. When diagnosis is suspected, MRI is the most useful investigation to demonstrate the extent of the lesion and the state of cord compression. Bone scan is useful to search for other sites of bone involvement. PET scan is useful to demonstrate sites of another organ metastasis. Histological diagnosis of specimens obtained through percutaneous biopsy or open surgery is ultimately needed for guiding treatment.
TREATMENT:
Treatments of spinal metastasis may include chemotherapy, radiotherapy, immunotherapy, and surgery. A combination of these methods is often needed. In considering spinal metastasis treatments, one must consider many factors.
a. Histogenesis:
This will determine the responsiveness of the tumour to chemotherapy, radiotherapy, hormonal or immunotherapy.
b. Extent of the metastatic lesion
This may cause spinal instability and cord compression if there is extensive tumour growth.
c. Other sites of spinal involvement or other organ metastasis
This indicates the extent of the disease.
d.The general health of the patient and the life expectancy
The patient’s condition may be so poor that surgical intervention becomes too risky.
e. Potential complications of the treatments recommended
Side effects of the recommended treatments have to be weighed against their benefits.
Roles of surgery:
a. Percutaneous biopsy
A CT guided needle biopsy for an accessible lesion has the advantage of being a minimally invasive procedure. However the yield may not be adequate to provide for a detailed histological analysis.
b. Open biopsy
In case of failed needle biopsy or when liberal amount of tissue specimen is critical, open biopsy should be employed
c. Percutaneous biopsy and vertebroplasty/kyphoplasty
Following biopsy, bone cement is injected into the vertebral body. This often gives good relief of pain. The procedure should be contemplated only if the wall of the vertebral body, especially posterior wall, remains intact. Otherwise there is the risk of bone cement leakage into the spinal canal.
d. Surgical decompression, instrumentation and fusion
Surgical approaches may be anterior or posterior. Sometimes a combination of both approaches is necessary. Surgery is needed if patient presents with deteriorating neurological deficit due to spinal cord compression, or when there is imminent risk of pathological vertebral fracture. Radiotherapy or chemotherapy may not be able to remove the tumour compressing the cord fast enough. They also can not address the pain arising from spinal instability due to pathological fracture. Speedy surgical decompression is needed in such circumstance to preserve the spinal cord function. Following surgery, patient will have good pain relief and can be treated with chemotherapy or radiotherapy without fear of losing the neurological function.
In summary, spinal metastasis is frequently diagnosed late and requires a high index of suspicion in order to reach early diagnosis.Histological diagnosis is critical for guiding the mode of treatment. Most of the spinal metastasis are treated with a combination of chemotherapy, radiotherapy, immunotherapy or hormonaltherapy. Vertebroplasty /kyphoplasty are useful for painful metastasis with inact po sterior vertebral wall. Open decompression surgery with spinal instrumentation is still needed in situation of spinal cord compression and instability from pathological fracture.
