Novel Case of Eruptive Keratoacanthomas Associated with Apalutamide Treatment for Prostate Cancer

Prostate cancer is the second most common cancer globally diagnosed in men1, with more than 160,000 new cases each year in the United States.2 Even with relatively high rates of survival, many deaths occur due to metastases. It most often metastasizes to bone, to other sites including lymph nodes, lungs, and liver as well.1,3 A wide range of treatment options are currently available — active surveillance, surgery, radiation, chemotherapy, and hormonal therapeutics.2 Although most patients experience remission with standard therapy, approximately 10-20% of prostate cancer cases are castration-resistant.4 Up to 16% of these patients show no evidence that the cancer has spread at the time of the castration-resistant diagnosis.4 Castration-resistance refers to continued tumor growth despite appropriate hormonal treatment. In February 2018, apalutamide, a nonsteroidal antiandrogen (NSAA), was approved by the Food and Drug Administration (FDA) as the first drug for non-metastatic castration-resistant prostate cancer.4 Recently, there have been cases reporting generalized eruptive keratoacanthomas (EKA) in association with use of the program cell death (PD-1) targeting drugs like nivolumab, pembrolizumab, and leflunomide when treating malignancy. 5,6,7 However, based on our literature review, we were unable to find documented cases involving apalutamide. We present the case of an 86-year-old Caucasian male with castration-resistant prostate cancer following radical prostatectomy diagnosed with biopsy-confirmed EKA with squamous cell carcinoma (SCC) two and a half months after the initiation of apalutamide.