Prospective noninterventional study on the use of panitumumab monotherapy in patients with recurrent or progressive colorectal cancer: the VECTIS study

PURPOSE Epidermal growth factor receptor-targeted monoclonal antibodies are active as monotherapy beyond second-line treatment. Skin toxicities (STs) are common during treatment, and a positive association between ST severity and patient outcome has been reported. This study collected information on panitumumab monotherapy use in patients with KRAS exon 2 wild-type metastatic colorectal cancer in clinical practice. METHODS This open-label, prospective, observational, noninterventional study included adult patients who had failed prior chemotherapy with 5-fluorouracil, oxaliplatin, and irinotecan. Patients received panitumumab monotherapy (6 mg/kg every 2 weeks) for ≤18 cycles. Effectiveness was assessed as disease control rate (DCR), tumor response, and freedom from progression. The incidence of ST and other adverse drug reactions (ADRs) was recorded, as were Eastern Cooperative Oncology Group performance status (ECOG PS) and quality of life. The KRAS analysis process was also evaluated. FINDINGS The full analysis set included 632 patients (64.6% male; mean age, 62.3 years), who completed a mean of 9.6 panitumumab cycles. ST, mainly grade 1/2, occurred in 84.3% of patients, 82.7% of whom required treatment. Nonskin ADRs occurred in 3.5% of patients. By the end of treatment, the DCR was 58.9% overall, and was 53.8% and 62.7%, respectively in patients with ST grade 0/1 and grade 2/3. Significant associations were observed between maximum ST grade and best response (P=0.0009), DCR (P=0.0046), tumor response (P=0.0002), and freedom from progression (P=0.0084). At the end of the study, 67.4% of the patients had an ECOG PS of 0/1. Quality of life was rated as "very good" or "good" in 70.3% of patients. Mean time to obtain KRAS results was 18.2 days; satisfaction with different aspects of KRAS testing was "very good" or "good" in 80%-97% of patients. CONCLUSION Panitumumab monotherapy showed adequate effectiveness and safety in patients with heavily pretreated KRAS exon 2 wild-type metastatic colorectal cancer. The most common ADR was grade 1/2 ST.