Objective: To evaluate the response to cetuximab, in terms of time passed until disease progression and overall survival, in patients with colorectal cancer (CRC) in which the epidermal growth factor receptor (EGFR) is undetectable.
Method: Nine EGFR-negative patients (confirmed by an immunohistochemistry study), who were being treated with cetuximab, were selected. Variables collected: demographic data, diagnosis, previous treatments, time since first metastasis to start of treatment with cetuximab, adverse events and tumour markers. The response was monitored using tumour markers and disease progression. Well-being was assessed using the Karnofsky performance status (KPS) or that of the Eastern Cooperative Oncology Group (ECOG).
Results: 22% men (2/9) with a median age of 48 (31-63). The median time from being diagnosed with the metastatic disease to the start of treatment with cetuximab was 19 months (12-48). All patients had failed an irinotecan-based regime, 77.77% (7/9) had also failed one which included oxaliplatin. The median number of cycles with cetuximab was 14 (6-32). The main adverse event was the appearance of an acneiform rash in 100% of the cases. The median time until disease progression was 7 months (3-16) and 10.2 months (4-24) for overall survival. The results for well-being showed a KPS of between 80-100% and an ECOG of < 2. The results obtained in the present study for overall survival and time until disease progression are higher than those in the pivotal study (10.2 compared to 8.6 months and 7 compared to 4.1 months respectively).
Conclusions: According to the results obtained, the use of assessing the EGFR expression (by the immunohistochemistry technique at least), as a means of predicting response to treatment with cetuximab may be questioned. This suggests that selecting patients using the routine assessment of this receptor is inappropriate, since it excludes patients who may potentially benefit from the treatment. However, more clinical trials are required in this area in order to confirm these conclusions.