Prospective analysis of UGT1A1 promoter polymorphism for irinotecan dose escalation in metastatic colorectal cancer patients treated with bevacizumab combined with FOLFIRI as the first-line setting.

Abstract

491 Background: Infusional fluorouracil/leucovorin plus irinotecan-based regimen (FOLFIRI) with bevacizumab has been widely used as first-line treatment for patients with metastatic colorectal cancer (mCRC). We prospectively analyzed the influence of uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) genotyping for irinotecan dose escalation in mCRC patients treated with combination of FOLFIRI and bevacizumab as the first-line setting. Methods: A total of 65 mCRC patients undergoing first-line treatment with FOLFIRI combined with bevacizumab were analyzed. Genotypes were performed by analyzing the sequence of TATA box of UGT1A1 of genomic DNA from the patients. Genotype and clinical parameters were compared by univariate analysis. The irinotecan dose is escalating form 180 mg/m2 to 260 mg/m2 in UGT1A1 6/6 or 6/7, and from 120 mg/m2 to 210 mg/m2 in UGT1A17/7. Results: The response rate was observed in 44 of 60 UGT1A1 6/6 or 6/7 (73.3%) in comparison to 1 of 5 UGT1A1 7/7 (20%) patients (p=0.013). The grade III-IV adverse events (AE) was observed in 4 of 60 UGT1A1 6/6 or 6/7 (6.7%) in comparison to 3 of 5 UGT1A1 7/7 (60%) patients (p<0.001), but it was not different between age of ≥ 70 and < 70 (p=0.559). Fifteen of 60 (20%) patients with UGT1A1 6/6 or 6/7 could be performed with liver or lung metastaectomy in comparison to none of 5 patients with UGT1A1 7/7. In addition, the disease control rate was significantly higher in irinotecan dose of ≥ 210 mg/m2 than irinotecan dose of < 210 mg/m2(p=0.015). Conclusions: UGT1A1 promoter polymorphism was found to be predictive of toxicity and efficacy in mCRC patients with first-line treatment of FOLFIRI combined with bevacizumab. The higher dose of irinotecan (≥ 210 mg/m2) may achieve a better disease control rate but do not increase the incidence of GR III-IV AE in mCRC patients of age ≥ 70 years.