Clinical and biochemical response following withdrawal of a long-acting, depot injection form of octreotide (Sandostatin-LAR (R))

OBJECTIVE Monthly injections of Sandostatin-LAR(R) have been shown to be an effective therapy for patients with acromegaly. Because of an ongoing need to assess a patients response to definitive therapy such as surgery and/or radiotherapy, we aimed to evaluate GH levels and acromegaly symptom scores in patients withdrawing from Sandostatin-LAR(R). DESIGN AND PATIENTS 12 patients with acromegaly previously treated with San dostatin-LAR(R), 20-40 mg intramuscularly every 28 (n = 9) or 42 (n = 3) da ys for 12-36 months were studied at monthly intervals for 4 months followin g the withdrawal of the drug. MEASUREMENTS Hourly fasting serum GH measurements between 0800 h and 1200 h , serum IGF-1 and symptom scores were undertaken at 4,8,12 and 16 weeks fol lowing the last injection of SandostatinLAR(R). MRI/CT scans of the pituita ry were undertaken at 16 weeks and compared to scans taken on Sandostatin-L AR(R) within the previous 10 months. RESULTS Serum GH rose progressively from 7.7 (1.5 to 14.6) (median (range)) mIU/l at 4 weeks to 9.9 (1.5-21.8), to 12.6 (4.9-31.9) (P < 0.05 vs 4 week s) and to 13.1 (6.0-39.1) mIU/l (P < 0.002) at 8, 12 and 16 weeks, respecti vely, following cessation of SandostatinLAR(R). IGF-1 rose from 38.5 (12.6- 73.8) nmol/l at 4 weeks to 62.4 (37.4-159) at 16 weeks (P < 0.002) and mean symptom score (comprising headache, sweating, arthralgia, paraesthesiae, t iredness) from 4.0 (0 to 10) (4 weeks) to 4.5 (0-9) (8 weeks) to 6.0 (2-10) (12 weeks) to 6.5 (4-12) (16 weeks, P < 0.05). Individual GH profiles indi cated a rise in GH in 5/12 patients between weeks 4-8 and between weeks 8-1 2 in a further 5/12 patients. There were no changes in pituitary tumour siz e following discontinuation of Sandostatin-LAR(R). CONCLUSIONS GH and symptom scores rise progressively following discontinuat ion of SandostatinLAR(R) in acromegalic patients. However, GH and symptom s cores remain suppressed in some patients for at least 8 weeks following ces sation of Sandostatin-LAR(R). We suggest that a withdrawal period of 3 mont hs from Sandostatin-LAR(R) is required in order to perform a meaningful re- assessment of GH and clinical status.