• Toshi Takaoka, Tetsuo Kimura, Rai Shimoyama, Shunji Kawamoto, Kazuki Sakamoto, Fuminori Goda, Hiroshi Miyamoto, Yuji Negoro, Akihito Tsuji, Koji Yoshizaki, Takahiro Goji, Shinji Kitamura, Hiromi Yano, Koichi Okamoto, Masako Kimura, Toshiya Okahisa, Naoki Muguruma, Yoshiro Niitsu, and Tetsuji Takayama.
• Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15, Kuramoto-cho, Tokushima, 770-8503, Japan.
• Cancer Chemother. Pharmacol. 2016 Aug 1; 78 (2): 397-403.

BackgroundIrinotecan plus S-1 (IRIS) is the only oral fluoropyrimidine-based regimen reported to be non-inferior to FOLFIRI and widely used in clinical practice for metastatic colorectal cancer (mCRC) patients. However, the combination of IRIS plus an anti-EGFR agent has not been evaluated previously. This study aimed to investigate the feasibility and efficacy of IRIS with panitumumab as second-line therapy for wild-type KRAS mCRC.MethodsMain inclusion criteria were patients with wild-type KRAS mCRC refractory to one prior chemotherapy regimen for mCRC, ECOG PS 0-2, and age ≥20 years. Patients received panitumumab (6 mg/kg) and irinotecan (100 mg/m(2)) on days 1 and 15 and S-1 (40-60 mg according to body surface area) twice daily for 2 weeks, repeated every 4 weeks. The primary endpoint was the feasibility of the therapy. The secondary endpoints were response rate (RR), progression-free survival (PFS), and overall survival (OS).ResultsA total of 36 patients received protocol treatment in eight centers. Of these, 23 patients (63.9 %) completed protocol treatment, demonstrating achievement of the primary endpoint. The most frequent grade 3/4 toxicities were diarrhea (16.7 %), acne-like rash (13.9 %), and neutropenia (11.1 %). The overall RR was 33.3 % (12/36). Of these patients, five underwent conversion surgery. Median PFS and OS were 9.5 months (95 % CI 3.5-15.4 months) and 20.1 months (95 % CI 16.7-23.2 months), respectively.ConclusionIRIS plus panitumumab has an acceptable toxicity profile and a promising efficacy in patients with previously treated wild-type KRAS mCRC. Accordingly, this regimen can be an additional treatment option for second-line chemotherapy in wild-type KRAS mCRC.

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