The predictive value of the IGF-1 level in acromegaly patients treated by surgery and a somatostatin analogue.

BACKGROUND We evaluated the predictive value of IGF-1 against hGH in the treatment outcome. MATERIAL AND METHODS A prospective study was undertaken of 47 patients (mean age 41.1 ± 12.9 years; 44 with macroadenoma and 3 with microadenoma), requiring treatment with octreotide LAR (SSLAR) following incomplete surgery. Concentrations of hGH and IGF-1 were measured three months after surgery and three, six, nine, 12, 18, and 24 months after introducing SSLAR. RESULTS Following surgery, respective median values of hGH and IGF-1 concentrations were 5.55 ng/mL (IQR = 7.1) and 512.7 ng/mL (IQR = 379.5). After six, 12, and 24 months of SSLAR treatment, median values of hGH decreased significantly: to 2.95 ng/mL (IQR = 5.5, p < 0.05), 2.95 ng/mL (IQR = 4.4, p < 0.05) and 2.00 ng/mL (IQR = 3.6, p < 0.001), respectively. After six, 12, and 24 months of SSLAR treatment, the respective median IGF-1 concentrations significantly decreased to 384.5 ng/mL (IQR = 312.2, p < 0.01), 323.0 ng/mL (IQR = 230.3, p < 0.001) and 334.0 ng/mL (IQR = 328.9, p < 0.01). The differences between median hGH and IGF-1 concentrations at 12 and 24 months were not significant. A statistically significant correlation was found between IGF-1 concentration prior to and after surgery (R = 0.61, p < 0.05) and prior to SSLAR treatment and IGF-1 concentration 24 months later (R = 0.49, p < 0.05). No such correlation was observed for hGH. CONCLUSIONS The level of IGF-1 prior to surgery and prior to SSLAR treatment is a better predictor of the treatment outcome than hGH. Octreotide LAR was most effective over the first 12 months of treatment. No further significant decrease of hGH or IGF-1 levels was observed past this period.