Penile Metastasis as a First Manifestation of Metastatic Castrate-Resistant Prostate Cancer: A Case Report and Review of Management Challenges.

INTRODUCTION: Penis is a rare site of metastasis of prostate cancer, with an incidence of 0.3%. Penile metastasis is often detected incidentally via imaging modalities. Symptomatic cases may present with penile nodules, deformity, or urinary symptoms, and a biopsy is required for confirmation. Treatment varies based on disease extent and patient condition, ranging from tumour-directed approaches (penectomy, radiotherapy) to systemic therapies. CASE PRESENTATION: A 69-year-old man with high-risk nonmetastatic prostate cancer (T3bN0M0) underwent pelvic radiotherapy and androgen deprivation therapy. Five months later, he presented with urinary difficulty and penile pain. Imaging revealed multiple nodules within corpora cavernosa, along with lung lesions suggesting metastatic disease. A biopsy confirmed penile metastasis from prostate adenocarcinoma (Gleason score 9). Following a multidisciplinary team discussion, penectomy was ruled out, and the patient underwent palliative radiotherapy (RT), 20 Gy in 5 fractions, followed by systemic chemotherapy with docetaxel and carboplatin. Despite four cycles of chemotherapy, the disease progressed into the lungs, and the patient's performance status declined. The patient was transitioned to palliative care and passed away 12 months after the diagnosis of penile metastasis. CONCLUSION: Penile metastasis from prostate cancer is rare but an aggressive entity with a median survival ranging from 6 to 18 months. Penile metastasis shall be in the differentials when patients present with priapism, penile pain, and urinary difficulty. Tumour-directed approaches, including surgery and RT, could be curative. Emerging therapies such as stereotactic body radiotherapy and PSMA-targeted radioligand therapy may improve outcomes for this rare and aggressive manifestation.