Stereotactic Body Radiosurgery for 121 Cases of Spinal Metastases Treated at M.D. Anderson Cancer Center

Reviewer: Arpi Thukral, MD
Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 23 de septiembre del 2008

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Presenter: E. L. Chang
Presenter's Affiliation: M.D. Anderson Cancer Center
Type of Session: Scientific

Background

 

·         Spinal metastases commonly develop in patients with cancer, and can often cause extreme back pain, weakness, autonomic dysfunction, and difficulty with ambulation. Furthermore, the risk of cord compression increases significantly in patients diagnosed with spinal metastases.
·         The incidence of spine metastases is increasing since patients with systemic cancer are living longer with chemotherapeutic improvement, and therefore have a higher risk of dissemination of their disease.
·         Traditionally, the established treatments for these patients have been steroids, pain medications, radiation therapy, and surgical resection, alone or in combination. 
o        In terms of radiation therapy, the mainstay of treatment for spinal metastases has been conventional external beam radiotherapy. 
·         The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. Its use for the treatment of spinal lesions has been limited by the availability of effective target-immobilizing devices for the spine.
·         Radiosurgery allows one to deliver a high dose of radiation to a target volume in 1-5 fractions, which may be more convenient than the multiple sessions required for conventionally fractionated RT.
·         More recently, improvements in imaging and radiation treatment planning, have lead to the development of extracranial radiosurgery for treatment of spinal lesions. This may allow for delivery of large radiation doses near radiosensitive structures such as the spinal cord.
·         The objective of this study was to prospectively report on cancer control and patient-reported outcomes for patients undergoing stereotactic body radiosurgery (SBRS) for spinal metastases. 

Materials and Methods

  • This is a prospective examination of outcomes of patients enrolled on an IRB-approved protocol involving stereotactic body radiosurgery for spinal metastases at a single institution using a CT-on-rails image guidance system. 
  • Patients were treated to their spinal metastases every other day using IMRT, initially to 30 Gy in 5 fractions. The protocol was later amended to allow patients to be treated to 27 Gy in 3 fractions. Spinal MRI was obtained at baseline, 3, 6, 9, 12 months, and every 6 months thereafter to assess progression free-survival (PFS). 
  • At the above time points, patients were also assessed by neurologic examination. 
  • To evaluate pain control and symptom interference, the Brief Pain Inventory (BPI) and the M.D. Anderson Symptom Inventory (MDASI) were administered to the patients at each follow-up visit.  
  • Acute toxicity data was also recorded and graded according to the NCI Toxicity Scale, version 2.0. 
  • Key eligibility criteria:
    • MRI demonstrated spinal metastases
    • KPS>40
    • Histologic diagnosis of a primary cancer
    • Maximum of 2 spinal sites that need to be treated
  • Key exclusion criteria: 
    • Cord compression requiring surgery
    • Previous irradiation to >45 Gy to the spinal metastatic site
  • Median follow up was 13.0 months.

Results

  • Between November 2002 and December 2007, 121 patients (136 spinal tumors) were treated on this protocol with SBRS. 
  • Median age = 60 years (range: 22-88 years).
  • Renal cell carcinoma was the most common histology seen, accounting for 35%  (n=43) of cases. Other histologies noted were lung, breast, melanoma, colon, and sarcoma. 
  • The KPS for the majority of patients was 80. 
  • The median tumor volume was 40.6 cc. 
  • Spinal metastases were most commonly found in the thoracic spine, accounting for 50% of cases. 
  • 27/127 patients were previously irradiated to the area; 17/127 patients had previous surgery; and 37/127 patients had both.
  • 6 months spinal metastasis PFS: 90%; 1 year spinal metastasis PFS: 84%
  • Median survival = 21.4 months; 1 year OS: 65%; 2 year OS: 42%
  • A significant reduction in pain was also seen at 4 weeks post-RT, which likely led to a significant reduction in other symptom interference scores.
  • 27% of patients were pain-free (pain score=0) at baseline; 50% were pain-free at 3 months; 59% were pain-free at 6 months, p=<0.001.
  • Grade 3 related toxicities of nausea, vomiting, diarrhea, dysphagia, neck pain, chest pain, and trismus were seen. No grade 4 toxicities were seen and no cases of radiation myelopathy were observed to date. 

Author's Conclusions

  • The use of SBRS for spinal metastases in this population has been shown to be a safe and effective treatment modality, with a high PFS of 90% at 6 months and 84% at 1 year. 
  • Acute toxicities were relatively infrequent and easy to manage, and no late complications have been found yet.
  • Case control studies or a randomized trial is warranted to evaluate the use of SBRS compared to conventional radiation therapy for the treatment of spinal metastases. 

Clinical/Scientific Implications

  • Radiosurgery for spinal metastases is a reasonable alternative to conventional radiation therapy as it allows one to deliver a high dose of radiation in a significantly shorter treatment time compared to conventional RT. In addition, this may lead to faster control of patients’ pain and symptoms.
  • This prospective protocol provides valuable information about the use of SBRS in the treatment of spinal metastases, a modality which has not been studied extensively in this patient population.  
  • Although the data shown by the authors on PFS and pain control seems promising, this is a prospective single arm study, and the clinical relevance of these results should optimally be tested in a Phase III randomized trial.  
  • Long-term toxicity data is still not available on SBRS for spinal metastases. Until this is achieved, conventional radiation therapy remains the standard of care for patients with spinal metastases, and patients should be treated with this technique with caution.
  • Patient selection will be key to determine use of this modality. The authors did not state clearly in their study how patients were selected for treatment, however a bias may have lead to the high median OS time of 21.4 months noted in this study. 


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