Background There are two highly selective antibodies to the epidermal growth factor receptor (EGFR): cetuximab (Ig G1 chimeric molecule) and more recently panitumumab (fully humanised IgG2 molecule). Not much information is available about the sequential use of these EGFRs.

Purpose To analyse chemotherapy treatment with EGFR in those patients treated with panitumumab following cetuximab and to describe the reason for that change.

Materials and methods Retrospective study including patients treated with panitumumab following cetuximab during 2009 and 2010. Information was obtained using an Oncofarm database. The authors reviewed clinical histories and collected age, sex, diagnosis, line treatment settings, before chemotherapy was administered, mono or combination treatment, number of cycles administered, wild type KRAS, adverse drug events and reason for change from cetuximab to panitumumab.

Results Data from 12 patients were studied (mean age 65 years, 83% men). 75% patients had metastatic colorectal cancer (mCRC) and 25% head and neck cancer (in these patients treatment with panitumumab is an off-label indication). In 25% of patients, panitumumab was administered in combination (17% taxol, 8% taxol-carboplatin, 8% FOLFOX, 8% FOLFIRI). Panitumumab was administered as 4th line treatment. Reasons for change were: 25% cutaneous toxicity, 16% progression, 16% toxicity and progression, 8% convenience for patients (cetuximab weekly vs panitumumab every fifteen days) 8% suffered hypersensitivity reactions. All patients had wild-type KRAS and treatment with panitumumab was stopped after an average of 6 cycles because of cancer progression.

Conclusions There are not too many patients to whom panitumumab was administered following cetuximab. This sequential treatment was related to progression of the illness and toxicity. There is no evidence to assess whether panitumumab following cetuximab could avoid cancer progression. However, more studies are needed.