SAT-436 Adjuvant Therapeutic Modalities in Acromegaly: Clinical Course and Factors Predicting Biochemical Controls

Background Although surgical resection is the first line therapy for acromegaly, many patients do not achieve biochemical remission after surgery and require the adjuvant therapy including medical treatment (somatostatin analogues; SSA, GH antagonist, and dopamine agonist), conventional radiotherapy, and gamma-knife surgery (GKS). Due to the limitations of rare disease, there are few studies evaluating the efficacy of each adjuvant treatment. In this study, we investigated clinical course and disease control after initiation of adjuvant treatment. Method We performed a single-center retrospective study including acromegalic patients treated with SSA at least for 6 months from January 1, 2005 to June 30, 2018. Age, gender, fasting GH, IGF-1 levels, 75 g oral glucose tolerance tests and tumor size were measured before/after operation, medical treatments, or radiotherapy. The patients were considered biochemically controlled/cured if fasting mean GH levels were less than 2.5ng/ml or nadir GH after oral glucose loading was less than 1 ng/ml together with age- and sex-matched normalized IGF-1. Result We analyzed 72 patients for median 62.9 months (40.0-111.5). The median age was 46 (37-53) years. The median duration of SSA use was 31.5 months (12.6-53.0). The median GH level was 30.5 (17.6-47.3) ng/ml, IGF-1 was 694.7 (600.0-862.8) ng/ml, initial tumor size was 24 (17.2-32.2) mm. Of 72 patients, 59 patients (81%) underwent surgical resection and 40 patients (55.6%) underwent GKS. Of the 40 patients who underwent GKS, 16 (40%) discontinued the medication after 26 (10.3-35.2) months. After treatment, 54 patients (75%) were biochemically controlled. Before initiation of SSA treatment, biochemically controlled group had significantly lower GH (3.63 vs 15.35ng/ml, p<0.001), IGF-1 (514.0 vs 641.9ng/ml, p=0.005), nadir GH after oral glucose loading (2.66 vs 7.9ng/ml, p<0.001) and basal glucose level (94.5 vs 104.5g/ml, p=0.098) than non-controlled group. There was no significant difference in tumor size and Hardy classification between biochemically controlled group and non-controlled group. Among the enrolled patients, 34 subjects (52.3%) had a size reduction of more than 10%. A group with a decrease in tumor size by more than 10% had a smaller initial tumor size (20.0 vs 29.5mm, p<0.001) and lower GH level (3.30 vs. 5.05 ng/ml, p=0.033). There was no significant difference in IGF-1, nadir GH, and basal glucose level. Conclusion In conclusion, basal GH level and presence of visible remnant tumor was correlated with biochemical response after adjuvant treatment. Appropriate adjuvant treatment should be decided according to the disease status of acromegalic patients.