Imaging of Nonfunctioning Pituitary Adenomas: The Cost of Surveillance

Introduction: Nonfunctioning pituitary adenomas are treatable but notoriously recurring entities that are frequently asymptomatic until late in their course. Most lesions can be safely and effectively treated through a minimally invasive transsphenoidal approach, but recurrent disease is common even several years after a gross total resection. As the potential visual compromise from these lesions can be devastating, they present a costly surveillance challenge to clinicians and patients. Annual MRIs are often recommended for surveillance. In this study, we sought to define the cost of this practice and to determine whether this was effective at reducing the long-term risk of vision loss.

Methods: After obtaining IRB approval, we retrospectively reviewed the records of 143 patients who underwent primary transsphenoidal resection of nonfunctioning pituitary adenomas at our institution between 2003 and 2011. Clinical history, visual field testing, operative reports, pathology and imaging data were reviewed. Magnetic resonance imaging (MRI) costs were estimated at $571.93 based on the Centers for Medicare and Medicaid (CMS) national average reimbursement for MRI brain with and without contrast. Differences between groups were compared via student's t-test, chi-squared and Fisher's exact test.

Results: One hundred twenty patients (57 male and 63 female) received between one and eleven (median = 2, mean = 3.20) surveillance MRI scans following their routine post-operative imaging for a total of 382 surveillance scans. The median interval between subsequent scans ranged from 249–382 days and the median total follow-up period was 47 months (range 3–123 mos). Recurrence or growth of residual tumor was detected in 37 (31%) of patients, additional growth was noted in 13 follow up scans in these patients, and 332 scans were stable. Estimated total cost of all surveillance scans was $218,477.30 and the cost per scan which revealed any growth was $4,369.55. Recurrence was significant enough to warrant treatment with a second surgery in 15 patients and radiation therapy in four. The cost to identify these 19 (16%) patients with clinically significant growth was $11,498.80 per patient. Overall, 5/19 patients (26%) with clinically significant growth experienced new visual field deficits prior to intervention. These patients had significantly longer mean intervals between scans than those who did not have visual deterioration (380 vs 1576 days, p = 0.00036). Additionally, patients who had imaging at greater than one year intervals were significantly more likely to develop new visual field deficits (p = 0.022) than those with annual imaging.

Conclusions: Recurrence or growth of residual occurred in one-third of our patients with nonfunctioning pituitary adenomas. Annual imaging was associated with preservation of vision in patients with clinically significant growth during our observation period. Although imaging is costly, we feel the nonlinear tumor growth curves and possible devastating visual consequences justify this cost. Given the association between regular follow up and preservation of visual function, future research should be aimed at improving patient follow-up.