Intralesional Methotrexate for the Treatment of Advanced Keratinocytic Tumors: A Multi-Center Retrospective Study

Introduction: Keratinocyte tumors (KT) are frequently observed. Surgery is the treatment gold standard. In some cases, a surgical approach might not be the best option. Radiotherapy (RT) and systemic treatments can frequently cause side effects or be contraindicated. Intralesional methotrexate (MTX) can be a conservative yet effective alternative. We decided to evaluate the effectiveness and safety of intralesional chemotherapy with MTX for the treatment of squamous cell carcinoma (SCC), keratoacanthoma (KA), and basal cell carcinoma (BCC). Methods: All patients had a histologically confirmed diagnosis of BCC, SCC, or KA and no indication to surgery or RT. MTX was injected subcutaneously proceeding from the periphery of the lesion toward the center. Different protocols in terms of dose, frequency, and length of treatment were used to compare them. Treatment efficacy was evaluated in terms of tumor size reduction. Patients were divided into three groups: responders (improvement of more than 50%), partial responders (< 50%), and non-responders (no improvement or worsening). All data were analyzed using the chi-squared test (χ2). Results: Thirty-five patients were included. Twenty-one patients suffered from SCC, 12 from KA, and 2 from BCC. KA showed a higher response rate than SCC and BCC. For AK, 92% of patients had a complete resolution; 8% were partial responders. For SCC, 47.6% of cases were responders and 14.3% partial responders, while 38% non-responders. All BCCs showed no improvement. A treatment protocol of weekly injections, performed for 4 to 6 weeks, was the most efficient. Doses of 25 mg/ml per session seemed to be most effective. About one third of our patients developed side effects with mild anemia being the most frequent. Conclusions: For selected cases, intralesional MTX can be a safe and effective option for the treatment of KT, especially in case of KA and, to a lesser extent, SCC.