Endocrine Abstracts

Introduction: Dopamine agonists (DA) effectively normalize prolactin secretion and reduce tumour size in most patients with macroprolactinomas. However, some patients are considered partially/totally resistant. Some authors propose that patients treated for 2 years, with normal prolactin secretion with low dose AD and maximal tumour diameter reduction >50%, could suspend treatment, but relapse rate is uncertain. Definition of resistance, ideal duration of treatment and criteria to evaluate reduction of tumour size have to be clarified.

Objectives and methods: Observational, analytical and retrospective study to assess the response of macroprolactinomas to DA in the first 2 years of treatment and define three groups of response based on prolactin levels and maximal tumour diameter reduction: resistant (high PRL,<10%); sensitive (normal PRL >50%) and partially resistant (PR) the remaining, and analyze their outcome.

Results: Fifty-two patients, 51.9% males; mean age at diagnosis 40.3±16.3 years; mean follow-up 6.8±4.1 years; 90.4% treated with bromocriptine, initial median dose 5.0 mg/day (P25–3.75 mg; P75-7.5 mg). After 2 years, 48% sensitive; 41.9% PR; 9.3% resistant. After 1-year, sensitive and PR patients normalized PRL in 85 and 50% and reduced tumour size >50% in 50 and 5.9% respectively. In both groups, PRL normalization didn’t improve significantly in the second year. This period was important for imagiologic response in sensitive (P=0.003), but not in PR (P=0.083). In resistant, there wasn’t significant improvement in either parameter after 2 years or afterwards (P=0.331). At follow-up, 19% of sensitive had withdrawn treatment, without recurrence. Although PR patients improved prolactin normalization (86.7%; P=0.016) and tumour reduction (>50%:53.3%; P=0.008) at follow-up, they still had a less favourable outcome.

Conclusion: In our series, biochemical response preceded imagiologic response. Therapeutic results after 2 years were already present at 1 year of treatment and were maintained afterwards. PR had a less favourable outcome at follow-up, making their identification important for earlier change of therapeutic approach.