Purpose: Dysregulation of the phosphoinositide 3-kinase (PI3K)/Akt/mTOR pathway is seen in 40% to 60% of patients with colorectal cancer. Everolimus, an oral inhibitor of mTOR, showed efficacy in patients with metastatic colorectal cancers in phase I studies.
Experimental design: In sequential phase II studies assessing two dosing schedules, patients with metastatic colorectal cancers refractory to bevacizumab-, fluoropyrimidine-, oxaliplatin-, and irinotecan-based regimens received everolimus 70 mg/wk (n = 99) or 10 mg/d (n = 100). Primary endpoints were disease control rate (DCR) and objective response rate; secondary endpoints included progression-free survival (PFS), overall survival (OS), and duration of response or stable disease (SD). Tumor tissue was collected from all patients for predefined exploratory biomarker analyses.
Results: Seventy-one patients were included in the per-protocol set for each cohort. DCRs of 31.0% and 32.4% (all SD) were seen in the weekly and daily schedules, respectively. Median duration of SD was 3.9 months in each cohort. Median PFS and OS were 1.8 and 4.9 months and 1.8 and 5.9 months, respectively, for the weekly and daily schedules. Among patients receiving daily everolimus, those with a KRAS mutation experienced significantly shorter median OS (P = 0.008) and lower DCR (P = 0.035) compared with those with wild-type KRAS in exploratory biomarker analyses.
Conclusions: Everolimus 70 mg/wk or 10 mg/d was well tolerated but did not confer meaningful efficacy in heavily pretreated patients with metastatic colorectal cancers. Future studies may consider evaluating everolimus in combination with other agents or in patients with dysregulation of the PI3K/Akt/mTOR pathway.