Background: Multiple modalities are available for the treatment of basal cell carcinoma (BCC). The most commonly used modalities include simple excision, Mohs micrographic surgery, curettage and electrodessication, cryosurgery, and irradiation therapy. Interleukin‐2 (IL‐2) is a cytokine produced chiefly by activated T lymphocytes and has effects on various components of the immune system. Until now the primary clinical use of IL‐2 has been in advanced stages of metastatic melanoma and renal cell carcinoma. Systemic administration of IL‐2 is known to cause significant toxicity.

Objective: The objective of this study was to evaluate the therapeutic efficacy and safety of perilesional PEG‐IL‐2 injections in patients with BCC in an open label, uncontrolled pilot study.

Methods: Patients with histologically confirmed primary BCC over 18 years of age were included in the study. Lesions were treated by injecting a total volume of 0.5 cc of IL‐2 in a radial fashion in the subcutaneous tissue. Injection dosages ranged from 3000 to 1,200,000 IU in one to four weekly dosages. A total of 12 tumors were treated in eight patients.

Results: Overall response rates were as follows: complete response in 8 of 12 treated tumors (66.6% cure rate), partial response in 3 of 12 injected tumors (25% partial response rate), stable disease with no improvement in 1 treatment site (8.4%). Side effects included local pain, swelling, and erythema, and in one patient flulike symptoms. There were no significant changes of blood tests as compared to baseline levels.

Conclusions: The therapeutic response induced by perilesional PEG‐IL‐2 injections was found to be an encouraging, safe, and well‐tolerated treatment of BCC. Further studies including a larger patient population and long‐term follow‐up are necessary in order to substantiate these findings.