Dopamine agonist medications are effective as a first-line therapy for invasive giant prolactinomas, because they can significantly shrink tumor volume and control the PRL level. Tumor mass vanishes in some patients after bromocriptine treatment; in other patients with localized residual tumor, stereotactic radiosurgery is a viable option so that unnecessary surgery can be avoided. The application of radiotherapy does not reliably shrink tumor volume.

Invasive prolactinomas are more likely to be resistant to drug therapy but the mechanism of this is still unknown. The objective of this study was to analyze the different expression of ERmRNA and D2RmRNA isoforms in prolactinomas responsive and resistant to dopamine agonist (DA), and to discuss the correlation of such gene expression with tumor biological behavior. A prospective study of 20 consecutive patients who harbored prolactinomas was designed. Patients were classified as responsive (14 cases) or resistant (six cases) according to their clinical and biochemical response to bromocriptine. Tumor tissue samples were examined by means of QRT-PCR analysis. Median D2SmRNA expression in responsive patients was about 2.5-fold that in resistant ones (13.5 +/- 10.4 and 5.4 +/- 2.4, respectively, P = 0.09). No significant difference was found between D2LmRNA expression levels (P = 0.77). However, there was a significant difference between D2S/D2LmRNA ratios for responsive and resistant tumors (P = 0.012). A significant difference was not found between these two groups in levels of ERalphamRNA and ERbetamRNA expression (P = 0.20 and 0.06, respectively). D2SmRNA expression was significantly different for invasive and noninvasive tumors (6.2 +/- 3.6 vs. 17.0 +/- 11.2, respectively, P = 0.02). The D2S/D2L ratio is related to the responsiveness of prolactinomas to DA medication, in which D2SmRNA plays an important role. Lower expression of D2SmRNA in invasive tumor patients suggests that invasive prolactinomas may be more likely to be resistant to DA medication.

About three-fourths of prolactinomas with CS invasion can be effectively controlled not only with regard to tumor volume disappearance but also in serum PRL normalization. Residual tumor in the CS areas with PRL normalization and no pressure symptoms can be treated with low-dose of bromocriptine so as to achieve long-term tumor volume control and endocrine control. Great attention should be paid to CS residual tumors accompanying the empty sella, especially in cases with optic chiasmal herniation.