Preoperative predictors of biochemical remission in somatotroph adenoma resections: a single-institution retrospective review

OBJECTIVE There is persistent debate in the literature surrounding the true predictors of biochemical remission after resection of somatotroph adenoma. A multimodal analysis of a large number of patients is needed to better understand which patients may be at higher or lower risk for remission failure after surgery. METHODS A retrospective review was performed on patients undergoing somatotroph adenoma resection. Biochemical remission was defined as age- and sex-adjusted normalization of serum insulin growth factor-1 (IGF-1) levels at least 6 months after surgery. Patient case characteristics and clinicopathologic variables were tested for statistical associations with remission and were included in a random forest machine learning model to assess for their importance in determining remission status. Preoperative variables found to be significant remission predictors on statistical testing and important in the random forest model were subsequently assessed via receiver operating characteristic (ROC) analysis to determine numeric thresholds that optimally predicted preoperative likelihood of remission success or failure. RESULTS Eighty patients were identified with somatotroph adenoma who underwent transsphenoidal resection, with 60 patients (75%) achieving biochemical remission. Statistical testing found that patients with failed remission were more likely to have larger tumors (1.9 vs 1.6 cm by the largest axis, p = 0.014; and 3.61 vs 2.66 cm 3 by 3D volume, p = 0.013) that invaded the cavernous sinus more frequently (70% vs 22% of patients, p < 0.001) and have higher preoperative IGF-1 level (860 vs 660 ng/ml, p = 0.044). An optimized random forest machine learning model with 10,000 iterations found that tumor size, preoperative growth hormone and IGF-1 levels, and cavernous sinus invasion were important preoperative predictors of remission status. ROC analysis revealed that 96% of patients with preoperative 3D tumor volume less than 1.51 cm 3 (area under the curve [AUC] 0.691, p = 0.003) and 100% with nonadjusted preoperative IGF-1 level less than 718.5 ng/ml (AUC 0.736, p = 0.002) achieved remission. CONCLUSIONS Important preoperative predictors of postoperative remission for somatotroph adenoma resection include serum IGF-1 level, cavernous sinus invasion, and tumor size. Ninety-five percent of patients who achieved postoperative remission had preoperative 3D tumor volume less than 1.51 cm 3 .