Prospective evaluation of argon gas probe delivery for cryotherapy of bone tumours.

INTRODUCTION: 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. MATERIALS AND 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. CONCLUSION: 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.