Gamma knife surgery for cancer pain-pituitary gland-stalk ablation: a multicenter prospective protocol since 2002.

OBJECT The authors have treated intractable pain, particularly cancer pain related to bone metastasis, with various protocols. Cancer pain has been treated by gamma knife radiosurgery (GKS), targeted to the pituitary gland-stalk, as an alternative new pain control method. The purpose of this study was to investigate a prospective multicenter protocol to prove the efficacy and the safety of this treatment. METHODS Indications for patient inclusion in this treatment protocol were: 1) pain related to bone metastasis; 2) no other effective pain treatment options; 3) general condition rated as greater than 40 on the Kamofsky Performance Scale; 4) morphine effective for pain control; and 5) no previous treatment with radiation (GKS or conventional radiotherapy) for brain metastasis. The authors at one institution have treated two patients, who suffered from severe cancer pain related to bone metastasis, by using GKS. The target was the pituitary gland. The maximum dose was 160 Gy with one isocenter of an 8-mm collimator, keeping the radiation dose to the optic nerve less than 8 Gy. At another institution two patients were treated in the same way; an additional five patients were treated similarly with targeting of the pituitary gland with two isocenters of 4-mm collimator. In all nine cases, pain resolved without significant complication. Pain relief was observed within several days, and this effect was prolonged until the day that they died. At a follow up of 1 to 24 months, no recurrences and no hormonal dysfunction were observed. CONCLUSIONS Despite insufficient experience, the efficacy and the safety of GKS for intractable pain were demonstrated in nine patients. This treatment has the potential to ameliorate cancer-related pain, and GKS will play a more important role in the treatment of intractable pain. More experience and additional refined study protocols are needed to evaluate which parameters are important, to determine what treatment strategy is the best, and to clarify the safest option for patients with intractable cancer pain.