The association between prolactin level variation and prolactinoma size reduction remains unclear. This study aimed to determine the prolactin level cut-off predictive of a tumor size reduction.
Retrospective cohort study.
We reviewed medical records of patients with prolactinoma who received primary cabergoline therapy and for whom complete data on pituitary hormone assays and sellar MRI at baseline and 3 months post treatment were available. We tested whether the certain prolactin level after 3 months post treatment predicted better response.
Prolactin levels normalized in 109 (88.6%) of 123 included macroprolactinoma patients. The mean tumor size reduction was 22.9%, and patients in the lowest prolactin tertile (≤0.7) had the highest frequency of tumor size reductions of ≥20% (73.7 vs 52.9% and 45.9% in tertiles 2 (>0.7 to 2.6) and 3 (>2.6 to 20), P = 0.015). Patients with prolactin levels ≤1 ng/mL exhibited larger tumor size reductions vs those with prolactin levels of 1–20 (27.2 ± 18.3% vs 19.5 ± 13.9%, P = 0.014), 1–10 (19.3 ± 13.7%, P = 0.017) and 1–5 ng/mL (19.2 ± 14.3%, P = 0.039). A multivariable logistic regression analysis revealed that a prolactin level ≤1 ng/mL at 3 months and high-dose cabergoline therapy were significantly associated with tumor size reductions of ≥20% (odds ratio (OR): 2.8, 95% confidence interval (CI): 1.2–6.7, P = 0.017; OR: 2.0, 95% CI: 1.0–3.9, P = 0.043).
A prolactin level ≤1 ng/mL at 3 months after cabergoline treatment was correlated with a significant tumor size reduction in patients with macroprolactinoma. This finding may help clinical decision making when treating macroprolactinoma patients.
Supplemental Table 1. Macroprolactinoma patients who achieved prolactin normalization after 3 months of cabergoline treatment, classified using a prolactin cut-off value of 5 ng/mL
Supplemental Table 2. Percentage of cases with size reductions of ≥20% among macroprolactinoma patients who achieved prolactin normalization after 3 months of cabergoline treatment, classified using a prolactin cut-off value of 1 ng/mL