Background and Importance Treatment with chimeric recombinant IgG1 (cetuximab) and human IgG2 (panitumumab) epidermal growth factor receptor (anti-eGFR) blocking antibodies, is associated with skin and subcutaneous tissue disorders in most patients.

This may result in the discontinuation of treatment in patients with stage IV colon cancer.

Aim and Objectives To evaluate skin toxicity and analyse tolerance to both anti-eGFR drugs.

Material and Methods An observational, retrospective, and descriptive study of patients treated with panitumumab or cetuximab in monotherapy or associated with chemotherapy between June 2020 – June 2022 was conducted in a tertiary hospital.

Safety was evaluated according to Cancer National Institute-Common Terminology Criteria for Adverse Events version 5.0(CNI-CTCAE-v5.0). The data collected were: sex, age, weight, location and grade of metastasis, Eastern Cooperative Oncology Group (ECOG), cycle and grade of the first episode of toxicity, and tolerance. The information was obtained from the Oncofarm^®program and the Diraya^® digital medical record. Data analysis was performed using the PASWStadistic18 statistical package.

Results Forty-two patients were evaluated, 21 treated with panitumumab and 21 cetuximab. 35/42 (80%) developed skin toxicity. Skin toxicity was more frequent in the panitumumab group than in the cetuximab group: 18 patients (87.5%) vs 17 (81%). The first skin reactions occurred in cycle 1, in 88.9% with panitumumab and in 64.7% with cetuximab. Grade 1 toxicity was observed in 21 patients (60%), mainly acne, being more frequent in the cetuximab group than panitumumab: 12 patients (70.6%) vs 9 (50%). However, 50% of the panitumumab group developed severe toxicities (grade 2–3), mainly xerosis and acneiform rash. No grade 4 toxicities were reported. Cetuximab was well tolerated in 70.6% of patients while panitumumab produce poor tolerance in 68%, causing treatment discontinuation due to severe skin toxicity in 11%. Adherence to preventive treatment measures (hydration, sun protection, topical formulations and/or antibiotic therapy) allowed the continuity of treatment, with disease progression being the cause of suspension in 47.6% (20 patients).

Conclusion and Relevance In this study, panitumumab has shown more aggressive toxicity than cetuximab. Good practice in preventive toxicity treatment is necessary for continuity of anti-eGFR therapy.

Conflict of Interest No conflict of interest