Insulin resistance, estimated by serum C-peptide level, is associated with reduced event-free survival for postmenopausal women in NCIC CTG MA.14 adjuvant breast cancer trial

524 Background: NCIC CTG MA.14 is a randomized multi-centre trial of tamoxifen versus combined tamoxifen and octreotide LAR therapy in the adjuvant treatment of breast cancer in post-menopausal women. Planned secondary analyses included investigation of baseline metabolic factors that might influence survival. Laboratory and clinical studies indicate that insulin resistance is associated with adverse outcome in breast cancer. Insulin resistance elevates C-peptide levels. Methods: In MA.14, trial patients with stage I or II postmenopausal breast cancer were randomized from September, 1996 until July, 2000 to receive 20 mg tamoxifen PO daily for 5 years with/without the administration of the somatostatin analogue Octreotide LAR 90 mg depot injection monthly for 2 years. Event-free survival (EFS), the trial’s primary outcome measure, was defined as time from randomization to time of recurrence of primary disease, time of second malignancy or death due to any cause. We investigated the effect of baseline IGF-...