Insulin growth factor-1 receptor (IGF-1R) expression in small cell lung cancer (SCLC).

Abstract

e21098 Background: SCLC is a highly aggressive form of malignancy in which limited therapeutic options exist and median survival remains dismal. Insulin Growth Factor (IGF) pathway is involved in endocrine, paracrine and autocrine control and it mediates its effect through IGF-1R. Elevated IGF-1 has been associated with increased risk of lung cancer, and it functions as a growth factor in SCLC. We studied the expression of IGF-1R in patients diagnosed with small cell cancer to determine expression pattern. Methods: This is a descriptive pilot study. Cases of small cell carcinoma diagnosed between 2000 and 2007 were identified from the tumor registry. Immunohistochemical (IHC) stains were performed on paraffin embedded tissue using an anti-IGF-1R (G11) rabbit monoclonal primary antibody (Ventana, AZ). Staining characteristics were documented using semi-quantitative criteria, and all slides were reviewed by a single pathologist. Results: Twenty four patients with adequate tissue were identified. The median age was 66 years, 12 were male, 12 were female, 21 patients had SCLC; 11 had extensive stage(E) and 10 had limited stage(L); 2 patients had small cell of the bladder (stage II) and one had small cell metastatic to cervical lymph node without primary site determined. The IGF-1R expression ranged from 0 to 4+ (5 had 0+, 9 had 1-2+ and 10 had 3-4+), median of 2. The percentage of cells positive for IGF-1R ranged from 0 to 90 % ( 5 had 0%, 19 had > 10% and 17 had ≥ 50%), median 70%. Of the 17 patients with 50% or more cells positive for IGF-1R; 8 had extensive stage and 7 had limited stage SCLC; 1 had bladder as the primary site and 1 had extrapulmonary small cell carcinoma. Conclusions: We conclude that IGF-1R is commonly expressed in both limited and extensive stage SCLC and is a potential therapeutic target in this disease. Clinical trials using an IGF-1R directed agent should be pursued. No significant financial relationships to disclose.