Skin/nail infections with the addition of pertuzumab to trastuzumab-based chemotherapy.

We report a series of breast cancer patients with invasive skin and nail infections with Staphylococcus species that we attribute to the addition of pertuzumab to trastuzumab-based therapy. With the suspicion of an increased incidence of cutaneous infection in patients treated with pertuzumab and trastuzumab-based chemotherapy, treating medical oncologists identified patients receiving therapy who experienced infection. Between March and October 2014, 18 patients treated with pertuzumab and trastuzumab-based chemotherapy were found to have 21 separate skin/nail infections. Treatment was administered as neoadjuvant therapy in 12 (67%) patients, adjuvant therapy in four (22%) patients, and for metastatic disease in two (11%) patients. Granulocyte growth factors were administered in 11 (61%) patients and no patients were documented to be neutropenic. New skin and nail lesions developed as early as cycle 1 and as late as 8 months from initial therapy. The 21 separate infections documented were folliculitis and "bite-like" lesions (10), abscess (6), paronychia (3), and cellulitis (2). The appearance of these lesions was distinct from typical EGFR-associated skin changes. When cultures were obtained, Staphylococcus species were isolated. Quantitative immunoglobulins were assessed in 14 (78%) patients and were abnormally low in six (43%) of these patients. The skin infections resulted in treatment delay in two (11%) patients and premature discontinuation of therapy in one patient. We believe that the skin/nail infections reported here in patients treated with the combination of pertuzumab and trastuzumab represent a previously unrecognized toxicity of adding pertuzumab to trastuzumab-based therapies.