Background Cetuximab is a chimeric monoclonal IgG specifically directed against epidermal growth factor receptors (EGFR).
Among the drug-specific toxic effects of cetuximab are hypomagnesemia (10% of patients), and effects related to the infusion (10%), but the most common toxicity during treatment with cetuximab is a skin reaction, manifesting in 80% of patients treated, and is very severe in 10–20% of these.
The epidermis consists of 90% keratocytes, rich in EGFR receptors, explaining the high incidence of skin toxicity. The presence and intensity of the skin reactions correlate favourably with the effectiveness of treatment and survival.
Purpose To evaluate the toxicity of cetuximab in clinical practice and the possible correlation with the response to treatment in terms of PFS (progression free survival).
Materials and methods A retrospective analysis was conducted on the clinical records of patients treated with cetuximab from January 2012 to June 2013, in two Sicilian cancer centres (study RG-SC). We evaluated the toxicity and PFS and compared them with the findings of the most authoritative RCTs (randomised controlled trials) conducted on cetuximab.
Results Among the medical records examined 35 treatments were considered evaluable. Skin toxicity of any grade was observed in 63% of patients; in the first line in 60% with FOLFIRI-cetuximab and 71% with FOLFOX-cetuximab, in the second line in 80% of treated patients. Comparing our results to the regimens as reported in RCTs, grade 3–4 skin toxicity in the first line FOLFIRI-cetuximab was found to have occurred in 18.7% of our patients compared with 10%, and with FOLFOX-cetuximab in 14.1% of our patients vs. 14.3% of the RCT. In second line treatment none of our patients had skin toxicity vs. 8.2% in the RCT.
From the correlation between the degree of skin toxicity and PFS between our study and the CRYSTAL study, it appears that dermal toxicity grade 0–1 went with a PFS of 7.2 or 5.4 months, the PFS for grade 2 was 11.7 vs. 9.4 and for grade 3 went with a PFS of 14.5 vs. 11.3 months, respectively. In our group of patients the length of treatment in patients with grade 4 dermal toxicity that caused interruption was 12.8 months.
Conclusions Skin toxicity is the main specific toxicity of cetuximab and requires careful monitoring. In fact, with appropriate control measures it is usually manageable and rarely becomes a cause of discontinuation of treatment. The results showed that in clinical practice in the two cancer centres in Sicily skin toxicity was observed in a smaller percentage of patients than in RCTs. The positive correlation between onset, degree of toxicity and PFS observed in RCTs was confirmed in our study group with better than evidence in the literature. The onset of skin toxicity and its aggressiveness can be considered as factors predictive of response in patients treated with cetuximab.
No conflict of interest.
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