A phase II study of panitumumab plus irinotecan for metastatic colorectal cancer with wild KRAS, resistant to fluoropyrimidine, oxaliplatin, and irinotecan in Japanese (OGSG1001).

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607 Background: Anti-epidermal growth factor receptor (EGFR) antibody therapy showed to be effective in treatment for metastatic colorectal cancer (mCRC) with wild KRAS. Especially, combination chemotherapy with anti-EGFR antibody plus irinotecan is expected more effective than anti-EGFR antibody alone, resistant to irinotecan. We conducted a phase II trial of panitumumab plus irinotecan for mCRC with wild KRAS resistant to fluoropyrimidine, oxaliplatin, and irinotecan in Japanese. Methods: Subjects were mCRC patients with wild KRAS, who showed resistance to fluoropyrimidine, oxaliplatin, and irinotecan and had measurable disease, ECOG PS 0-2. Panitumumab (6 mg/kg) plus irinotecan (same dose as prior irinotecan) was administered every two weeks. This treatment was provided until progression. The primary endpoint was response rate (RR). Secondary endpoints were disease control rate (DCR), progression-free survival (PFS), overall survival (OS), response duration, and adverse event (AE). Results: A total of 31 subjects were enrolled between July 2010 and July 2012. Median age was 64 years old (range 42-74). Nineteen patients had liver metastasis, 11 had lung metastasis, and 3 had lymph node metastasis. An independent review committee evaluated for efficacy in eligible 31 subjects in accordance with the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. The RR of primary endpoint was 29.0% (95% confidence interval (CI), 14.2-48.0 %). DCR was 74.2% (95%CI, 55.4-88.1%) and median PFS was 5.6 months.(95%CI: 3.4-8.7) In 31 subjects for safety evaluation, the incidence of any Grade 3 or greater adverse events was 58.1%. Major adverse events of grade 3 were diarrhea (19.4%), rash acneiform (12.9%), fatigue (9.7%), anorexia (9.7%). A sudden death and an infusion related reaction were occurred. Conclusions: Combination chemotherapy with panitumumab plus irinotecan was demonstarated to be safe and more effective than Japanese single arm phase II of panitumumab alone for mCRC, resistant to fluoropyrimidine, oxaliplatin and irinotecan. This result in Japanese is equal to other reports of panitumumab plus irinotecan. Clinical trial information: UMIN000003819.