VALIDATION STUDY OF A PROGNOSTIC CLASSIFICATION SYSTEM IN PATIENTS WITH METASTATIC COLORECTAL CANCER WHO RECEIVED IRINOTECAN-BASED SECOND-LINE CHEMOTHERAPY

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Abstract

Background

Previously, five prognostic factors (ECOG PS 2, pathologically poorly differentiated adenocarcinoma, peritoneal metastasis, PFS of first-line therapy <6 months, and LDH >400 IU/l) were identified in 124 patients with metastatic colorectal cancer who received irinotecan-based second-line chemotherapy (Shitara K, et al. ASCO-GI 2009). Patients were categorized into three prognostic groups (low-risk = no factors, intermediate-risk = 1 factor, high-risk = 2 or more factors), with significant differences in median overall survival (23.5, 14.6, and 5.5 months, respectively). The purpose of this study was to validate this prognostic classification in an external validation cohort.

Methods

We retrospectively analyzed 198 patients with metastatic colorectal cancer who received irinotecan-based second-line chemotherapy after first-line oxaliplatin-based chemotherapy in three institutions. This was our validation cohort.

Results

The median overall survival of this validation cohort was not significantly different from that of the generating cohort (12.1 versus 14.6 months; P = 0.47). The distribution of the three prognostic groups in the validation cohort was as follows: low-risk (n = 68; 35%), intermediate-risk (n = 80; 41%), high-risk (n = 45; 23%). The MST of each groups showed significant differences (19.8, 11.0, 7.9 months; P < 0.01), as was shown for the generating cohort. A similar tendency was observed for progression-free survival.

Conclusions

Our results validated the previously defined prognostic classifications in patients with metastatic colorectal cancer who received irinotecan-based second-line chemotherapy. Further validation in prospective studies is warranted.

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