Apalutamide-induced lichenoid reaction in a patient with non-metastatic castrate-resistant prostate cancer.

Apalutamide is an oral selective androgen receptor inhibitor, approved by the FDA for the treatment of patients with non-metastatic, castration-resistant prostate cancer (M0 CRPC) at high risk of developing metastases and for patients with metastatic castration-sensitive prostate (mHSPC) in association with androgen deprivation therapy (ADT). In the registration studies, skin reactions were reported among the most common side effects and as an adverse event of special interest. Apalutamide-induced rash includes a wide spectrum of different types of skin reactions, but few cases reports and case series have described this adverse event. Here, we report an M0 CRPC patient who experienced a rare skin adverse event, a lichenoid reaction. After 4 months of therapy with apalutamide, the patient reported dorsal pricking and dry skin. Lichenoid reaction was confirmed histologically and its correlation to the drug was demonstrated after pursuing a multidisciplinary approach. To our knowledge, this is one of the first cases of Apalutamide-related lichenoid reaction and this clinical case showed the relevance of a multidisciplinary management when assessing drug-related adverse events. A broader knowledge of the spectrum of drug-related reactions would allow for a better diagnosis and therapy management by both physicians and patients.