Prognostic significance of the Ki-67 labelling index in GH-secreting pituitary adenomas

Objective. A single prognostic parameter useful to distinguish acromegalic patients at major risk of recurrence after adenomectomy is still not available. Taking into account the correlation between Ki-67 and the recurrence rate of pituitary adenomas, we studied the clinical outcome of acromegalic patients in relation to the expression of Ki-67 by the tumour tissue. Materials and methods. Study population : 39 newly-diagnosed acromegalic patients submitted to adenomectomy from 2000 to 2005. Before surgical procedure, and during the post-surgical follow-up, all patients performed a hormonal evaluation by assessment of serum IGF-I levels and GH suppression after OGTT and a radiological examination with MRI. Extrasellar extension or invasiveness of surrounding structures by the adenoma was evaluated by the neurosurgeon during adenomectomy. Each tissue sample taken from the adenoma was submitted to immunohistochemistry in order to detect Ki-67 expression. Patients were divided as following: group 1 with Ki-67 values  1% and group 2 with Ki-67> 1%. Patients were given medical therapy with somatostatin analogs in case of persistence of disease. Results. The two groups did not differ in terms of age at diagnosis, sex, tumour size, pre-surgical GH and IGF-I levels, post-surgical GH levels, tumour invasiveness or extrasellar extension Percentage of patients cured after adenomectomy was higher in group 1 (p<0.05); post-surgical IGF-I levels and percentage of recurrence of disease at neuroradiological follow-up were higher in group 2 (p