Abstract 930: Treatment patterns and overall survival among men with metastatic castration-resistant prostate cancer harboring DDR mutations
Authors: Solit David B. , Mettu Niharika B. , McCall Shannon J. , Dhawan Mallika , Bobbili Priyanka J. , DerSarkissian Maral , Ivanova Jasmina , Arondekar Bhakti , Chang Jane , Niyazov Alexander , Lee Jocelyn , Huq Risha , Green Michelle , Turski Michelle , Muthukumar Aruna , Guo Tracy , Duh Mei Sheng , Oh William K. 
Published: April 2023

Abstract
Background: Limited information is available about treatments and clinical outcomes among men with metastatic castration-resistant prostate cancer (mCRPC) whose tumors harbor DNA damage repair (DDR) mutations.
Methods: This retrospective chart review study included men diagnosed with mCRPC with ≥1 DDR mutation detected by tumor comprehensive genomic profiling who began a line of therapy on or after July 1, 2014, at oncology centers in the American Association for Cancer Research (AACR) Project Genomics Evidence Neoplasia Information Exchange (GENIE) consortium. The index date was the initiation of a new therapy in this period, in patients who developed castration-resistant disease and progressed while receiving androgen deprivation therapy. Data on all available lines of therapy post-index were collected. Outcomes reported include time to treatment discontinuation for any reason (TTTD) and overall survival (OS), which were assessed using Kaplan-Meier analyses. Results for tumor response-related endpoints are forthcoming.
Results: A total of 138 patients with mCRPC met the inclusion criteria. The mean age at index was 68 years, and 76% of patients were White. The median follow-up time was 27.1, 15.9, 11.3, and 9.4 months for 1L, 2L, 3L, and 4L+ therapy, respectively. Common sites of metastases included bone (74%), lymph nodes (69%), and lungs (10%). Common tumor DDR mutations included CDK12 (48%), BRCA2 (23%), ATM (21%), and BRCA1 (8%). Assessment of germline mutations was conducted in 114 (83%) patients; the most common was BRCA2 (8%). First-line (1L) treatment information was available for 119 (86%) patients, 2L for 101 (73%), and 3L for 75 (54%) patients. Novel hormonal therapy (NHT; 55%) and taxane chemotherapy (20%) were most common in 1L. Enzalutamide (35%) and abiraterone acetate (14%) were the most frequently used NHTs. Compared to 1L, the proportion of patients receiving NHTs was lower in 2L (33%) and 3L (17%), while the proportion of patients receiving taxanes was higher (36% in 2L and 31% in 3L). In 3L, poly ADP-ribose polymerase (PARP) inhibitors were used in 21% of patients. Median TTTD was 5.6 months (95% CI: 4.2, 7.2) in 1L, 3.9 months (95% CI: 3.0, 4.6) in 2L, and 4.0 months (95% CI: 3.3, 4.7) in 3L. Median OS was 36.3 months (95% CI: 30.7, 47.8) from the start of 1L, 21.1 months (95% CI: 15.6, 29.3) from the start of 2L, and 14.1 months (95% CI: 9.5, 20.5) from the start of 3L.
Conclusions: These findings provide real-world insights about treatment patterns and clinical outcomes among patients with mCRPC harboring DDR mutations. Such insight may provide a helpful benchmark for research aimed at improving clinical outcomes, particularly in later lines of therapy.
Citation Format: David B. Solit, Niharika B. Mettu, Shannon J. McCall, Mallika Dhawan, Priyanka J. Bobbili, Maral DerSarkissian, Jasmina Ivanova, Bhakti Arondekar, Jane Chang, Alexander Niyazov, Jocelyn Lee, Risha Huq, Michelle Green, Michelle Turski, Aruna Muthukumar, Tracy Guo, Mei Sheng Duh, William K. Oh. Treatment patterns and overall survival among men with metastatic castration-resistant prostate cancer harboring DDR mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 930.