Endocrine Abstracts

Background: Cabergoline is effective in achieving normoprolactinaemia and tumour shrinkage in about 70% of patients with macroprolactinoma. Only a few studies have followed-up the adenoma shrinkage for periods >2 years;the need for continuing imaging thereafter is not certain.

Aim: To evaluate tumour volume changes in patients with macroprolactinoma responsive to cabergoline during a long follow-up period.

Patients and methods: MRIs of 15 patients(14♂) with macroprolactinoma and mean follow-up 53.6±24.4 (range 24–97) months were reviewed. Inclusion criteria:achievement of normoprolactinaemia on cabergoline. Exclusion criteria:previous pituitary surgery/radiotherapy or treatment with other dopamine agonists.

Results: Baseline median prolactin: 37 565 mU/l (2586–573 200). Median final cabergoline dose: 5 mg/week (1–4), median time for normoprolactinaemia: 4 months (1–9.5).

Follow-up imaging was available for the first 21–37 (median 28) months in all cases. During this interval, all subjects showed significant tumour shrinkage (baseline median 742.1 mm³ (188.3–7531.2) vs 21–37 months assessment median 129.4 mm³ (20–2573); P<0.01). Ten cases had scans for a total of 42–97 (median 66) months. Overall, there was no difference between tumour volume at 2 years and at last assessment (median 126.2mm³ (20–2573.2) vs 81.5 mm³ (11–2791.9); P=0.11). Compared with baseline, at year 1 mean shrinkage was 68.3%, at year 2 77.6%, at year 3 80.8%, at year 4 81.3%, at year 5 84.3%. The yearly percentage volume change was significant between years 1 and 2 (P<0.05) but not thereafter (P=0.09–0.27). One patient had tumour enlargement despite normal prolactin (volume at 28 months:123 mm³-at 59 months: 170.7 mm³, 38.8% enlargement), which was however, not associated with clinical manifestations.

Conclusions: Macroprolactinomas responsive to cabergoline show dramatic shrinkage in the first 2 years of treatment. Afterwards, further volume alterations are not significant and imaging can be avoided (unless the clinical and biochemical picture changes) until checking for drug withdrawal at 5 years, if indicated.