Poor Correlation of Serum Α-Subunit Concentration and Magnetic Resonance Imaging Following Pituitary Surgery in Patients with Nonfunctional Pituitary Macroadenomas

Abstract

To review the clinical utility of measuring serum alpha-subunit as a marker for residual tumor in a group of patients with surgically resected nonfunctional pituitary adenomas. In this retrospective cross-sectional chart review using the pituitary database at the Cleveland Clinic, we identified patients with nonfunctional pituitary macroadenomas over a 4-year period (2000-2004) and selected those patients who had an elevated alpha-subunit concentration measured before pituitary surgery. Presurgery and post-surgery measurements of alpha-subunit, luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone were documented. Findings from preoperative and postoperative pituitary magnetic resonance imaging (MRI) were reviewed. We identified 54 patients who were evaluated for nonfunctional pituitary macroadenomas during the study period. Of the 39 who underwent pituitary surgery, 34 had a serum alpha-subunit concentration measured before surgery. Eight of 34 patients had elevated preoperative alpha-subunit levels with a median value of 1.8 ng/mL (range, 1.0-3.4 ng/mL). Of the 8 patients, 7 had follow-up MRI a median of 12 months (range, 6-52 months) after surgery. One patient was lost to follow-up. Three of 7 patients had persistently elevated alpha-subunit levels postoperatively; in 2 of these 3, MRI did not identify residual tumor. Among the 4 patients with postoperative normalization of alpha-subunit, 2 patients had residual tumor on MRI. The discrepancy between alpha-subunit levels and postoperative MRI calls into question the value of routine alpha-subunit measurement as a tumor marker in patients with nonfunctional pituitary macroadenomas.