Phase II trial of panitumumab with irinotecan as salvage therapy for patients with advanced or recurrent colorectal cancer (TOPIC study)

Little is known about the clinical impact of salvage panitumumab with irinotecan for metastatic colorectal cancer (mCRC) patients. The present study conducted a single-arm, multicenter phase II trial for mCRC with skin toxicity prevention program. The subjects were mCRC patients with wild-type KRAS, who showed resistance to fluoropyrimidine, oxaliplatin and irinotecan. Panitumumab was administered at a dose of 6 mg/kg every 2 weeks by intravenous infusion over 60 min, and irinotecan was administered at a dose of 100-180 mg/m²every 2 weeks by intravenous infusion over 90 min, depending on the preceding treatment dose. To prevent skin toxicities, a moisturizer was applied and oral antibiotics (100 mg minocycline twice daily) were initiated for 6 weeks. The primary endpoint was the response rate (RR) determined by independent reviewers. Secondary endpoints were the disease control rate (DCR), progression-free survival (PFS) time, overall survival (OS) time and adverse events. A total of 35 patients were enrolled between October 2010 and March 2012. The median age was 61 years (range, 41-76 years), with 25 male and 10 female patients. The initial irinotecan dose was 150 mg/m²in 19 patients and 180 mg/m²in 1 patient. The remaining patients were treated with ≤120 mg/m². A central review indicated a partial response in 8 patients (22.9%) and stable disease in 6 patients (17.1%), with an RR of 22.9% (95% confidence interval, 12.1-39.0) and a DCR of 40%. The RR of the patients with standard-dose irinotecan (150 or 180 mg/m²) was 30%, although that of low-dose irinotecan (100-120 mg/m²) was 13%. The median PFS time was 2.7 months, and the median OS time was 6.3 months. A grade 3 or above acne-like rash developed in 25.7% of patients. In conclusion, panitumumab and irinotecan as salvage therapy for mCRC KRAS wild-type patients with skin toxicity prevention exhibits limited efficacy. In particular, the effect of low-dose irinotecan with panitumumab appears to be clinically insignificant. Routine use of skin toxicity prevention is currently under evaluation.