The value of an acute octreotide suppression test in predicting response to long-term somatostatin analogue therapy in patients with acromegaly

Context: The usefulness of the acute octreotide test in the selection of patients with acromegaly for chronic somatostatin depot analogues treatment is controversial.
Aims: To determine the efficacy of acute octreotide suppression test (OST) in predicting response to long-term somatostatin analogue (Octreotide-long-acting repeatable, OCT-LAR) therapy in patients with acromegaly.
Settings and Design: Prospective study (2006-2007) conducted at a tertiary healthcare centre in western India.
Materials and Methods: Sixteen drug-naive patients with active acromegaly (postoperative±post radiotherapy) underwent 50 µg subcutaneous OST. Ten patients were treated with OCT-LAR for one year. Remission was defined as a nadir growth hormone (GH) < 1 ng/ml during 75 g oral glucose tolerance test (OGTT) (0, 10, 30, 60, 120, 180 min) and normal age, sex-matched insulin-like growth factor 1 (IGF1) levels.
Statistical Analysis: SPSS Software Version 11 was used for data analysis.
Results: Using GH cutoff < 1 ng/ml, four patients (40%) achieved control at 12 months, while five patients (50%) achieved normal IGF1 values. The mean basal GH levels in 10 responsive, four controlled and six uncontrolled patients were 34.7±61.14, 4.5±1.3 and 54.8±74.2 ng/ml respectively which suppressed to mean nadir GH of 3.75±4.03, 0.66±0.15 and 5.8±4 ng/ml respectively. Sensitivity, specificity, negative and positive predictive value for nadir GH < 1 ng/ml reached after an OST was 100% each in predicting remission in our cohort. Odds for control increased if the baseline GH was low (< 5 ng/ml in our cases).
Conclusions: Nadir GH < 1 ng/ml following an OST is a useful predictive marker of achieving disease remission with long-term OCT-LAR therapy.

Keywords
Acromegaly, octreotide suppression test, octreotide test dose, remission prediction, somatostatin analogue