Transsphenoidal surgery for acromegaly: endocrinological follow-up of 98 patients

Transsphenoidal surgery is the preferred treatment modality for growth hormone (GH)-secreting pituitary adenomas. In many series, the reported postoperative remission is based mainly on achievement of GH levels less than 2 ng/ml. Strict criteria for insulin-like growth factor I normalization and even lower GH levels (<1 ng/ml) are now suggested to define cure of acromegaly, but the evidence does not yet support such low GH levels in epidemiological follow-up. We analyzed our postoperative results in a large cohort of patients with acromegaly.

Ninety-eight patients harboring GH-secreting adenomas (46 microadenomas and 52 macroadenomas) underwent transsphenoidal surgery between 1990 and 1999. Ninety-one patients were operated for the first time, and 12 patients underwent reoperations because of previous surgical failure (7 had undergone surgery elsewhere previously). Biochemical remission was defined as a repeated fasting or glucose-suppressed GH level of 2 ng/ml or less, and a normal insulin-like growth factor I level.

Remission was achieved in 74% of all patients after one operation, including 84% of patients with microadenomas and 64% of patients with macroadenomas. Seventy-three percent of patients with macroadenomas 11 to 20 mm in size achieved remission, as compared with a 20% remission rate for patients with adenomas larger than 20 mm. Patients with preoperative random GH levels lower than 50 ng/ml had a better outcome (85% remission), whereas GH greater than 50 ng/ml was associated with remission in 30% of the patients. Only one of the patients (8%) with postoperative active disease who underwent a second operation achieved remission. Recurrence was rare (one patient), and all failed surgical attempts could be detected during the immediate postoperative evaluation.

On the basis of strict postoperative GH and insulin-like growth factor I criteria to define remission, our series demonstrates the efficacy of transsphenoidal surgery for acromegalic patients with microadenomas and noninvasive macroadenomas. However, patients with large adenomas (>20 mm) and preoperative GH greater than 50 ng/ml have a poor prognosis and require adjunctive medical or radiation therapy to control GH hypersecretion.