Macroprolactinomas: longitudinal assessment of biochemical and imaging therapeutic responses

To assess biochemical and imaging therapeutic response rates, when these occur and their predictive factors in patients with macroprolactinomas treated with dopamine agonists (DA).

Retrospective, longitudinal study of patients with macroprolactinomas treated with DA for ≥12 months.

prolactin normalization, reduction in maximum tumor diameter ≥50% and time until therapeutic responses.

We included 67 patients; 49.3% females, with median age at diagnosis of 43 years, 61.2% only treated with bromocriptine, 10.4% only with cabergoline, and 28.4% with both DA. Median follow-up time was 73 months. Prolactin levels normalized in 87%, mostly during the first 2 years. Prolactin levels after 6 months (HR 0.994, p = 0.012), 1 year (HR 0.970, p = 0.003), and 2 years (HR 0.970, p = 0.015) predicted its normalization time. Only 62% of the patients achieved a ≥50% reduction in maximum tumor diameter. Percent tumor diameter reduction after 1 year (OR 1.098, p = 0.022) and 2 years (OR 1.102, p = 0.008) predicted a ≥50% size reduction. Size reduction occurred later than prolactin normalization. Initial tumor diameter (HR 1.050, p = 0.032) and its percent reduction at 6 months (HR 1.110, p = 0.002), 1 (HR 1.060, p < 0.001), 2 (HR 1.045, p < 0.001), 3 (HR 1.048, p = 0.002), and 4 years (HR 1.074, p = 0.042) predicted the time until imaging response.

A significant number of patients did not obtain an imaging response. Biochemical and imaging responses were asynchronous and occurred mainly in the first 4 years of treatment. This may allow an earlier identification of partially resistant and resistant macroprolactinomas, with consequent change in the therapeutic approach.