title: Prospective evaluation of argon gas probe delivery for cryotherapy of bone tumours.
abstract: BACKGROUND
  Cryosurgery for tumoural ablation traditionally involves instilling liquid nitrogen into a tumoural bed. The inability to control precise delivery can result in potentially disastrous consequences of skin necrosis and nitrogen gas embolism. In this study, we evaluated a probe-based closed cryosurgical system, which eliminates these risks.
  
  
  METHODS
  We performed a prospective evaluation of 36 cases of bone tumours treated with a probe-based cryosurgical system at the National University Hospital, Singapore. Cases consisted of patients with benign aggressive tumours (42%), primary malignant bone tumours (25%) and bone metastases (33%). In primary bone tumours, the aim of therapy was cure. In bone metastasis, the aim of therapy was palliation defined as the relief of symptoms for the patients' remaining lifetime.
  
  
  RESULTS
  In the primary bone tumour group, no recurrences were reported. In the metastases group, where the intention was palliation, there were 3 cases of radiological relapses (P = 0.02) and 2 clinical relapses. Kaplan-Meier evaluation showed a statistically significant tendency for radiological relapse in metastatic disease versus primary disease (P = 0.02). Median time for relapse free survival in the metastatic group was 17 months (P = 0.01). There were 4 deaths in the metastatic group due to progression of disease unrelated to the index region of cryosurgical treatment. There were no deaths in the primary bone tumor group. We had 2 complications from this therapy involving fractures through the cryoablated segments. One case healed spontaneously and the other was most expediently managed with a shoulder hemiarthoplasty. There were no skin burns or embolic complications.
  
  
  CONCLUSIONS
  Good clinical efficacy with probe delivered cryotherapy has been shown in this group of 32 patients with cure in all primary disease. Relapse occurred in only a small proportion of patients with bone metastasis.
authors.affiliation: University Orthopaedic Hand and Reconstructive Microsurgery Cluster, National University Health System, Singapore 119228.
authors.forename: Chin Tat
authors.initials: CT
authors.lastname: Lim
authors.forename: Liza B K
authors.initials: LB
authors.lastname: Tan
authors.forename: Saminathan S
authors.initials: SS
authors.lastname: Nathan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001128:Argon; D001859:Bone Neoplasms / Q000401:mortality / Q000601:surgery*; D003452:Cryosurgery / Q000379:methods*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010166:Palliative Care / Q000379:methods; D011446:Prospective Studies; D012846:Singapore; D013223:Statistics as Topic; D055815:Young Adult
chemical_list: D001128:Argon