Endocrine Abstracts

Background: Octreotide LAR is a long-acting somatostatin analogue used in the management of metastatic neuroendocrine tumors (NETs), with antiproliferative and symptom control effects. It requires intramuscular (IM) injection. Missed IM injections can cause subcutaneous nodules (SCNs) on radiologic images. We reviewed the rates of SCNs in a real-world cohort of NETs receiving octreotide LAR and explored treatment outcomes.

Methods: Patients with gastrointestinal (GI) NETs commencing octreotide LAR between August 5, 2010 and March 8, 2018 at a single cancer center in British Columbia were identified from pharmacy records. Patients were included if they had a computed tomography (CT) scan performed at the time of progression and available preceding imaging for review. Fisher’s exact test was used to examine predictors of SCNs and Kaplan-Meier curves summarized differences that were compared with log-rank tests in progression free (PFS) and overall survival (OS).

Results: Of 243 GI NETs receiving octreotide LAR, 45 patients had all CT imaging at one site and were available for central review. Median age was 67 years, 53% were female, and SCNs were found in 44% (20/45) of patients. A higher proportion of patients with SCNs were female (65%), although this was not statistically significant (OR 2.36, 95% CI 0.66-8.29, P=0.23). Patients over 60 years were numerically but not statistically less likely to develop SCNs than younger patients (OR 0.47, 95% CI 0.15-1.68, P=0.34). The mean skin-to-muscle distance and body mass index (BMI) in patients with and without SCNs was 54mm vs 35mm and 29kg/m² vs 26 kg/m² respectively. There was a significantly increased risk of developing SCNs in patients with a skin-to-muscle distance over 38mm (i.e. the length of the Octreotide LAR needle) (OR 5.09, 95% CI 1.39-16.6, P=0.02) and a trend towards increased risk in obese patients (BMI over 30kg/m²) (OR 5.71, 95% CI 1.26-23.4, P=0.06). PFS (HR 1.01, 95% CI 0.56-1.78, P=0.98) and OS (HR 0.86, 95% CI 0.41-1.8, P=0.70) was similar between those with and without SCNs.

Conclusion: Almost half of patients receiving octreotide LAR for GI NETs may develop SCNs, and this is more likely in those with a higher skin-to-muscle distance. Despite this, there was no difference in survival seen between patients with/without SCNs. Factors such as female sex, younger age and obesity may affect body fat distribution and SCN development, and should be considered by clinicians when choosing a somatostatin analogue.

Abstract ID 23383