Epidermal growth factor receptor (EGFR) is overexpressed in many tumor types,[1] which makes it an ideal target for biologic and small molecule–targeted agents. Dermatologic toxicity with EGFR inhibitor (EGFRI)-associated agents can manifest in many forms. The most common form is a papulopustular reaction (PPR),[2-5] which can range from mild discomfort to a fulminant pustular eruption, and can lead to serious complications.
Pharmacists are not only charged with the dispensing, admixture, administration, and monitoring of these therapies, but are also becoming more involved in the recognition, diagnosis, and treatment of these dermatologic toxicities from this new class of agents. More challenging is the evidence that the degree of PPR may reflect the degree of efficacy of therapy. This development means that PPR (and other dermatologic toxicities) will become a routine problem in patients treated with these agents, making supportive therapy for these effects part of the treatment plan. A precise grading system will become necessary, as well as a better treatment plan for managing all grades and forms of these complications.
The "newness" of these agents makes potential complications difficult to recognize. All patients experience some degree of PPR—usually grade 1 or 2. However, some cases of PPR can be severe and challenging to manage. Although designated an "acneiform" or "acnelike" rash, it is treated much differently than the typical eruptions we see with acne vulgaris. Typically, dermatologic manifestations of acne vulgaris are best managed with drying agents such as benzoyl peroxide(Drug information on benzoyl peroxide). This therapy, however, is not used with EGFRI-associated PPRs. We are discovering that the process of eruption and fading is more of a drying process, and we must moisturize EGFRI-associated PPR to make the patient more comfortable during the time it develops, waxes, and wanes. In this article, we describe some of the agents used to treat the dermatologic toxicities commonly seen with EGFRI-associated therapy.
Topical Emollients
Caution should be exercised in selecting topical gels and lotions that contain alcohol(Drug information on alcohol) or alcohol-type drying agents. Again, this PPR is a "drying" rash, requiring more of an emollient-type agent to keep the drying, brittle eruptions well moisturized. Ointments, creams, bath oils, and soap substitutes are the most common types of emollients recommended by dermatologists to make the PPR more bearable. Cetaphil cleanser and Eucerin lotion are two popular over-the-counter emollients. Baths that incorporate Aveeno oatmeal products also have a soothing benefit.
Another important consideration for patients is the fact that sunlight may exacerbate the PPR. Patients should be counseled on the use of sunscreens and protective clothing. Numerous sunscreen products are on the market with moisturizers in their formulas, thereby providing protection from the sun as well as much needed moisture to the skin. Products that protect from both ultraviolet A and ultraviolet B radiation—that is, agents containing zinc oxide(Drug information on zinc oxide) or titanium dioxide—should be preferred. Patients should be encouraged to stay out of the sun, if possible. However, when they must venture outdoors, they should be cautioned about following the appropriate measures to protect themselves from the sun.
Antibiotics
Antibiotics, both systemic and topical, are often utilized to treat EGFRI-related PPR. Oral tetracyclines—specifically, minocycline(Drug information on minocycline) and doxycycline(Drug information on doxycycline)—are most often employed in treatment. Both of these drugs seem to have efficacy in treating PPR. Most often, the selection of agents seems to be based on the clinician's experience.
Minocycline has been associated with a rare, drug-induced, lupus-type syndrome, hepatitis, and hyperpigmentation, as well as vestibular changes that can lead to dizziness and loss of balance (minocycline package insert, 2006). Dosage is frequently 100 to 200 mg/d, and the drug can be taken with food or milk to minimize gastrointestinal (GI) toxicity. Doxycycline has been associated with a rare exfoliative dermatitis and, more importantly, photosensitivity. Dosage is usually 100 to 200 mg/d, and although patients should be instructed to take the drug on an empty stomach, it does present problems with GI irritation. Administration with food can decrease absorption of the drug up to 20% (doxycycline package insert, 2006). Of all the tetracyclines, doxycycline has the least affinity for calcium, and when the drug is taken with milk or antacids, gastrointestinal toxicity can be minimized.
Topically, metronidazole(Drug information on metronidazole) and clindamycin(Drug information on clindamycin) are the two agents most commonly used. Success with metronidazole in this setting is thought to be the result of the similarity of EGFRI-associated PPR to inflammatory rosacea, for which metronidazole is also very effective. The cream or lotion preparations of these agents should be prescribed, to take advantage of the cream/lotion base (often a water-in-oil emulsion), which can aid in moisturization. The use of the topical solution or gel formulations should be avoided due to the alcohol content, which can enhance dryness.
