Cetuximab: Targeted Therapy for EGFR-Positive Cancers
Cetuximab is an innovative antineoplastic agent consisting of a recombinant chimeric monoclonal antibody (IgG1) that specifically targets the epidermal growth factor receptor (EGFR).
The drug's mechanism of action is based on its high-affinity binding to the extracellular domain of the EGFR. This blockade prevents the binding of endogenous ligands (such as epidermal growth factor and transforming growth factor-alpha), thereby inhibiting receptor activation and subsequent intracellular signaling pathways (including the Ras-MAPK and PI3K-Akt cascades). This results in cell cycle inhibition, suppression of angiogenesis (formation of new tumor blood vessels) and metastasis, and stimulation of apoptosis (programmed cell death) in cancer cells.
Furthermore, cetuximab exhibits significant immunological activity by inducing antibody-dependent cell-mediated cytotoxicity (ADCC), directing the immune system's effector cells to specifically destroy tumor cells expressing EGFR.
Indications
Cetuximab is used for targeted therapy of malignant neoplasms with confirmed EGFR expression:
- Metastatic Colorectal Cancer (mCRC):
- In combination with irinotecan-based or oxaliplatin-based chemotherapy.
- As monotherapy in patients who have failed or are intolerant to previous irinotecan- and oxaliplatin-containing regimens.
- Critical Requirement: The drug is effective only in patients with RAS (KRAS and NRAS) wild-type tumors. Cetuximab is not indicated if mutations in these genes are present.
- Squamous Cell Carcinoma of the Head and Neck (SCCHN):
- In combination with radiation therapy for locally advanced disease.
- In combination with platinum-based chemotherapy for recurrent or metastatic disease.
- As monotherapy for patients who have progressed following platinum-based chemotherapy.
Dosage and administration
The drug is administered strictly by intravenous infusion under the supervision of an oncologist experienced in targeted therapy. The dose is calculated based on the patient's body surface area (BSA).
- Loading (initial) dose: 400 mg/m² of body surface area. Administered as a slow infusion over 120 minutes.
- Maintenance (weekly) dose: 250 mg/m² of body surface area. Administered weekly, with an infusion duration of 60 minutes.
- Premedication: Antihistamines and, in some cases, corticosteroids must be administered before each infusion to reduce the risk of infusion-related reactions.
- Administration details: The recommended infusion rate should not exceed 10 mg/min. The drug must not be administered as an intravenous bolus!
- Dose modification: In the event of severe skin reactions, therapy should be temporarily suspended. Once symptoms resolve, treatment may be resumed, potentially at a reduced dosage.
The use of cetuximab is impermissible in the following clinical situations:
- Hypersensitivity: Severe allergic reactions (Grade 3 or 4) to cetuximab or any of its excipients.
- RAS Mutations: Presence of KRAS or NRAS mutations when treating colorectal cancer (therapy will not only be ineffective but may also worsen the prognosis).
- Pregnancy and Lactation: EGFR plays a vital role in fetal development; therefore, the use of anti-EGFR antibodies is not recommended. Breastfeeding should be discontinued during therapy and for 2 months after the final dose.
- Pediatric use: Safety and efficacy in children and adolescents under 18 years of age have not been established.
- Combination with oxaliplatin: Contraindicated in patients with mutant RAS type.
Cetuximab therapy is frequently associated with specific side effects related to its mechanism of action:
- Dermatologic reactions (over 80% of cases): Development of acne-like rash, pruritus (itching), dry skin, skin fissuring, and infectious complications. The severity of the rash often correlates with therapeutic efficacy.
- Infusion-related reactions: Chills, fever, and dyspnea (shortness of breath). In rare cases (approximately 1%), severe anaphylactic reactions may occur, usually during the first infusion.
- Electrolyte disturbances: Decreased blood magnesium levels (hypomagnesemia), requiring regular laboratory monitoring and, if necessary, supplementation.
- Ocular symptoms: Conjunctivitis, blepharitis, keratitis, and increased lacrimation.
- Respiratory system: In very rare cases, interstitial lung disease may develop.
- General reactions: Fatigue, nausea, diarrhea, and elevated liver enzymes.
