e17022 Background: De novo SCPC and tNEPC in metastatic castrate resistant prostate cancer (mCRPC) are rare, aggressive cancers with a poor prognosis. After first-line (1L) platinum chemotherapy (PLT), there is no consensus on 2L treatments. This multi-institutional, retrospective study examines practice patterns among clinicians and evaluates the outcomes of patients (pts) with SCPC or tNEPC in the 2L setting. Methods: After IRB approval, pts with a pathologic diagnosis of SCPC or tNEPC (any % of SC or NE histology defined by institutional review) were identified. Pts diagnosed between 2000-2020 who received 1L PLT and any 2L systemic therapy (tx) for SCPC or tNEPC were included. Standardized data collection templates containing demographic, clinical, and pathologic variables were collected. The primary endpoint was objective response rate (ORR) to 2L tx. Secondary endpoints included PSA response, time on 2L treatment, and overall survival (OS) from time of 2L tx. Data was analyzed using descriptive statistics. Results: Forty-two pts (21 SCPC, 21 tNEPC) from 6 institutions were included. At SCPC/tNEPC diagnosis, the overall cohort had a median age of 65.0 years (IQR 60.5, 68.0) and median PSA of 3.0 ng/dL (IQR 0.5, 21.8). The most common sites of metastasis included lymph node (78.6%), bone (54.8%), and liver (52.4%). For 1L tx, 37 pts (88.1%) received PLT and 5 (11.9%) had PLT + immunotherapy (IMM). For treatment to the prostate, 21 (51.2%) had none, 7 (17.1%) radiation (RT), 9 (22.0%) surgery, 3 (7.3%) RT + surgery, and 1 (2.4%) brachytherapy alone. Concurrent ADT was given to 32 pts (76.2%) in the 1L and 2L. At last follow-up, 34 pts (81.0%) were dead, 4 (9.5%) were alive, and 4 (9.5%) were lost to follow-up/censored. For 2L tx, 10 pts (23.8%) received PLT, 8 (19.0%) taxane monotherapy (TAX), 10 (23.8%) IMM, 8 (19.0%) other chemotherapy (CHX), and 6 (14.3%) other tx. Among 38 pts evaluable for response, the ORR was 15.8% (6 pts with PR: 4 PLT, 1 IMM, 1 CHX). PSA response ≥ 50% to 2L tx was seen in 5 of 29 pts with PSA data (17.2%). Other outcomes data are reported in Table. Conclusions: In this retrospective study, pts with SCPC or tNEPC who reached 2L tx received a wide variety of treatment regimens, reflecting the lack of consensus in this tx setting. ORR was low and overall prognosis was poor in the 2L regardless of tx choice. Pts on 2L immunotherapy seemed to have the shortest mOS. [Table: see text]
Read full abstract