Difference in survival outcomes between de novo vs therapy-related neuroendocrine cancer of prostate (NCP): A SEER-based analysis.

e17167 Background: Neuroendocrine cancer of prostate (NCP) is an aggressive histological subtype of prostate cancer with poor prognosis and lack of effective therapeutic agents. These can either arise de novo or secondary to hormonal therapies of prostate adenocarcinoma due to lineage plasticity. There have not been many studies comparing the difference in outcomes of these two subtypes of NCP. Methods: We retrospectively examined the SEER 17 registry November 2023 (SEER Stat 8.4.4) and used the multiple primary session to identify therapy-related neuroendocrine cancer of prostate (t-NCP) with a primary site recode ICD-O-3/WHO 2008 of 619 (Prostate) and histological codes (8140) for prostate adenocarcinoma. Secondary prostate malignancies with histological codes 8012, 8013, 8020, 8021, 8041, 8042, 8045, 8240, 8246, and 8574, all indicating neuroendocrine tumors were identified. De novo NCP were identified by excluding t-NCP from all NCP by unique ID numbers. Missing values were imputed using multiple imputations, and baseline characteristics were compared using Chi-square test or Mann-Whitney U test. Analysis was performed using Cox proportional hazards model to identify covariates and Kaplan-Meier survival curves to identify difference in survival. Analysis was conducted using Stata 18.0. Results: A total of 1400 de novo NCP and 143 t-NCP were identified. The median age range of the population was 72 years (IQR-62-77). The population comprised of 83.5% White, 9.6% Black or African American, and 5.9% Asian or Pacific Islander population. There was no significant difference between the baseline characteristics (age, staging characteristics, chemotherapy received, radiation received, surgery received) between the two groups. The median overall survival was 11 months vs 8 months in the de novo vs t-NCP group (p<0.05). A Cox proportional hazards model revealed that radiation therapy (HR=0.82, CI-0.74-0.93 ;p=0.001) and surgical treatment (HR=0.85, CI-0.81-0.88 ;p<0.001) were associated with better survival while t-NCP subtype (HR=1.33, CI-1.10-1.62;p=0.003), unit increase in age group (HR=1.11, CI-1.08-1.15; p<0.001), and unit increase in staging(HR=1.43, CI-1.30-1.57; p<0.0001)were associated with poorer survival. Chemotherapy did not have a significant impact on outcomes (HR=0.940, p=0.298). Conclusions: Outcomes were worse in t-NCP compared to de novo NCP. Besides, while radiation therapy and surgery showed improved outcomes, no such effect was observed in chemotherapy. Baseline characteristics of de novo vs t-NCP. De novo NCP t-NCP p-value Age(median) 72(62-77) 72(62-77) 0.8337 1 Chemotherapy received 50.70% 53.80% 0.475 2 Radiation received 31.20% 24.40% 0.272 2 Surgery received 32.40% 30.07% 0.083 2 Stage 4 disease 23.08% 21.86% 0.2153 1 1-Mann-Whitney U test, 2-Chi-square test.