Biochemical recurrence (BCR) among patients (pts) with prostate cancer (PC) after radiation therapy (RT).

Abstract

e17111 Background: RT is a frequent primary treatment for pts with clinically localized PC. Despite its frequent success, 30-50% of pts eventually present with BCR, defined as rising prostate-specific antigen (PSA). BCR is associated with a higher risk of developing distant metastasis and ultimately death from PC. Understanding BCR occurrence and its impact on clinical outcomes is important for optimizing diagnostic and therapeutic strategies for recurrent disease. Methods: This is a retrospective cohort study using nationally representative Electronic Medical Records (EMR) data from Optum© from 1/2010-9/2021. Eligible pts were adults who underwent RT after PC diagnosis, had ≥ 3 available PSA values after initiating RT, and had EMR activity for at least 6 mo before and 12 mo after RT. Pts with a history of prior malignancy except nonmelanoma skin cancers and pts with metastatic PC (mPC) at baseline (BL) or within 3 months after RT were excluded. The BL period was 6 mo before RT initiation. Primary outcome was frequency of BCR, defined as rising PSA (PSA ≥ nadir + 2 ng/mL); secondary analyses included % of pts who progressed to mPC, castration-resistant PC (CRPC), and death after BCR and factors impacting time to BCR. Results: 9,292 RT pts were included in this analysis. Key pt characteristics/outcomes are shown in the Table. Median (range) age was 69.0 (40-88) y, 83.2% of pts were White, and 13.4% were Black. Median PSA nadir was 0.11 ng/mL, 32.5% of pts had received androgen deprivation therapy (ADT) during BL period, and median (Q1-Q3) follow-up from RT initiation was 3.8 (2.4-5.7) y. Overall, 10.2% of pts developed BCR. Among BCR pts (n = 949), 51.2% had a PSA doubling time (PSADT) < 6 mo and 16.9% had a PSADT between 6-10 mo; 35.0% developed mPC, 30.2% developed CRPC, and 23.4% died. In multivariate Cox regression models, the BL factor associated with the highest risk of developing BCR was PSA ≥ 20 ng/mL. Conversely, the risk of developing BCR was lower for pts who received ADT during BL. Conclusions: This real-world (RW) study evaluates BCR occurrence in pts who underwent RT with a curative intent from a large US database. The study confirms BL PSA as an important prognostic marker for BCR, while use of ADT before RT is associated with a lower risk of BCR. A considerable % of pts with BCR developed mPC (35%) or died (23%) during the study period. Novel treatment strategies are needed to delay BCR and further progression to advanced PC in pts with high-risk localized disease. [Table: see text]