Long-term IGF-1 monitoring in prolactinoma patients treated with cabergoline might not be indicated

Purpose Cabergoline (CAB) therapy for prolactinomas has been associated with serum IGF-1 levels modifications, with recent reports indicating a paradoxical increase of IGF-1 levels during ongoing therapy. As a result, IGF-1 measurement has been proposed not only at diagnosis of a prolactinoma, but also during follow-up. In this follow-up study on prolactinoma patients with chronic CAB therapy, we investigated whether there are long-term changes in IGF-1 levels that necessitate continuous monitoring. Methods We reviewed our institutional database on prolactinoma patients with long-term CAB therapy, in whom IGF-1 levels were measured at baseline, at 3-months follow-up and in the long term. Results Chronic CAB therapy was noted in 20 patients (13 men, 7 women). Median (+/- SD) age was 43.5 +/- 12.6 years. 17 (85%) patients presented with a macroprolactinoma. Median CAB treatment time was 75 +/- 43 months (range 24-187). Median IGF-1 levels increased at last follow-up, though not significantly; from 122 +/- 37 ng/ml (IQR 104-160 ng/ml) to 133 +/- 54 (IQR 121-162 ng/ml), p = 0.10. Thereby, 18 (90%) patients showed normal serum IGF-1 levels adjusted for age, one (5%) patient above (1.05 x ULN) and 1 (5%) patient below the normal range (0.34 x ULN). No patient was or became symptomatic of acromegaly. Conclusion Our long-term results indicate that chronic treatment with CAB in prolactinoma patients does not significantly modify serum IGF-1 levels. Bearing in mind the sample size of this study, continuing IGF-1 monitoring is not indicated in prolactinoma patients with long-term CAB therapy.