Serum biomarker analysis in a phase II study of irinotecan in refractory metastatic breast cancer (MBC).

Abstract

Abstract Abstract #6074 Objective: To analyze blood-serum biomarkers (HER2, EGFR, uPA, and TIMP-1) for prediction of response to treatment in conjunction with Study 96-32-55, a multicenter phase II trial assessing the efficacy and tolerability of two irinotecan schedules in anthracycline- or taxane-refractory MBC patients.
 Methods: MBC patients who experienced disease progression after one to three chemotherapy regimens, including at least one anthracycline- or taxane-based regimen, were randomly assigned to irinotecan in 6-week cycles comprising 100 mg/m2 weekly for 4 weeks, then a 2-week rest or 240 mg/m2 every 3 weeks. During this study the serum samples from each patient were collected at a possibility of three time points; prior to treatment, at the first occurrence of response, and at completion of or withdrawal from treatment. Response prediction was analyzed using predetermined elevated/non-elevated serum biomarker cutoffs. Percentage changes from baseline to first response and disease progression were analyzed.
 Results: In the weekly arm, the objective response (CR+PR) rate was 23% (95% CI, 13% to 37%), and in the every-3-weeks arm, the objective response rate was 14% (95% CI, 6% to 26%). Serum biomarker levels were determined for HER2, EGFR, uPA, and TIMP-1 prior to treatment for 91 patients. Of these 91 patients, 17 had serum measurements at first response, and 38 had serum measurements at their completion of study due to disease progression. Only 7 patients had serum-levels collected at all three event-points. The baseline levels of sHER2, EGFR, uPA, and TIMP-1 were not different among responders and non-responders (Fisher's Exact p=0.41, 0.26, 0.68, 0.75). sHER2 level increased by 20.6% from baseline to disease progression (p=0.01). TIMP-1 level was 15.2% lower than baseline at first response (p=0.03), 16.5% higher than baseline at disease progression (p=0.01), and for 7 patients with all three event-point measures, TIMP-1 was 21.8% lower than baseline at first response and was 22.3% higher than baseline at disease progression (p=0.02, 0.04).
 Conclusions: In this study, serum levels of HER2, EGFR, uPA, and TIMP-1 do not appear to be predictive of response. However, interpretation of the data is compromised due to limited availability of serum at all 3 points. Serum HER2 appears higher at disease progression than at baseline. Serum TIMP-1 appears to decrease from baseline to first response, and then appears to increase at disease progression. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6074.