Panitumumab in combination with irinotecan plus S-1 (IRIS) as second-line therapy for metastatic colorectal cancer.

BACKGROUND

Irinotecan 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.

METHODS

Main 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).

RESULTS

A 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.

CONCLUSIONS

IRIS 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.