Young-onset prostate cancer in the real world: A single-institution cohort of 126 patients diagnosed before age 55.

e17136 Background: Prostate cancer diagnosed before the age of 55 years is considered early-onset disease and represents a distinct clinical subgroup with limited real-world evidence. We report clinical characteristics, treatments, and outcomes of a large cohort of young patients treated at Instituto Oncológico Henry Moore (IOHM). Methods: All patients in the IOHM database with biopsy-confirmed prostate cancer diagnosed before age 55 between October 1, 2012, and October 1, 2025, were identified. Patients were followed in person or by telephone until death or January 2026. Clinical, pathological, treatment, and outcome data were analyzed. Results: Median age at biopsy was 51 years (range: 42-54). Diagnosis occurred through screening in 70 patients (55%) and due to symptoms in 56 (45%). Gleason scores were 6 (n = 51), 7 (n = 39), 8 (n = 14), 9 (n = 19), and 10 (n = 3). Disease stage at diagnosis was stage I in 48 patients, stage II in 39, stage III in 12, and stage IV in 27 patients (21%). A first-degree family history of prostate or breast cancer was present in 20 patients (15%). Fifty-two percent were current or former smokers, 30% had hypertension, and 31% were obese (BMI > 30). Three patients with stage I Gleason 6 disease opted for active surveillance. Radical prostatectomy was performed in 63 patients and radiotherapy in 25 patients. All patients received systemic therapy (hormonal therapy with or without chemotherapy) according to ASCO and NCCN guidelines. Median follow-up was 64 months (range: 2-169). Median time to progression and overall survival decreased with advancing stage, with stage IV patients showing 29 and 38 months, respectively. Recurrence after radical prostatectomy occurred in 21 of 63 patients (33%). Overall survival did not differ by mode of detection or initial local treatment. Table 1 shows the evolution of patient population by stage. Conclusions: 1. This represents the largest single-institution cohort of young patients with prostate cancer reported in Argentina. 2. Twenty of 126 patients (15%) had a first-degree family history of prostate or breast cancer. 3. In 70 patients (55%), the tumor was detected through screening. 4. Sixty-three of 99 patients with early-stage tumors (63%) were treated surgically. 5. Only 3 of 32 patients with stage I, Gleason 6 disease opted for active surveillance. 6. Time to progression and estimated survival in young patients with advanced tumors treated according to current recommendations are very short, highlighting the need for more effective therapeutic strategies for this patient population. Patient population evolution by stage. Characteristic Stage I Stage II Stage III Stage IV Total patients 48 39 12 27 Pt with disease progression 8 16 4 20 Deaths 4 3 3 19 Estimated time to progression (months), Kaplan-Meier 146 113 108 29 Estimated overall survival (months), Kaplan-Meier 169 150 120 38