Management of medically refractory prolactinoma

Abstract

Resistance to dopamine agonists is defined here as failure to normalize prolactin levels and failure to decrease macroprolactinoma size by ≥50 %. Failure to normalize prolactin levels is found in about 25 % of patients treated with bromocriptine and 10-15 % of those treated with cabergoline. Failure to achieve at least a 50 % reduction in tumor size occurs in about one-third of those treated with bromocriptine and 10-15 % of those treated with cabergoline. Treatment approaches for patients resistant to dopamine agonists include changing to another dopamine agonist and increasing the dose of the drug as long as there is continued response to the dose increases and no adverse effects with higher doses. Transsphenoidal surgery is also an option. Clomiphene, gonadotropins, and GnRH can be used if fertility is desired. For those not desiring fertility, estrogen replacement may be used unless there is a macroadenoma, in which case control of tumor growth is also an issue and dopamine agonists are generally necessary. In many patients modest or even no reduction in tumor size may be acceptable as long as there is not tumor growth. Hormone replacement [estrogen or testosterone] may cause a decrease in efficacy of the dopamine agonist. Reduction of endogenous estrogen, use of selective estrogen receptor modulators, and aromatase inhibitors are potential experimental approaches. Temozolomide may be useful as a last resort for aggressive, invasive tumors refractory to other medical and ablative therapies.