280P - Radium-223 for patients with metastatic castration-resistant prostate cancer with symptomatic bone metastases progressing after first-line abiraterone or enzalutamide: One institutional experience

Background

Abiraterone (ABI) and enzalutamide (ENZ) are preferred as 1st-line therapy for mCRPC. Ra-223 has survival impacts for mCRPC with symptomatic bone mets but no benefit in combination with ABI/ENZ. Very few pts wanted to receive chemotherapy due to old age and could not afford NGS or PSMA scan. 40% pts received Ra-223 as 2nd-line therapy after ABI/ENZ and lymph nodes (LNs) < 3 cm in short-axis were enrolled in the ALSYMPCA trial. We reported the outcome of mCRPC pts with bone mets receiving Ra-223 as 2nd-line therapy after ABI/ENZ.

Methods

We collected data that pts using ABI/ENZ as 1st-line therapy for mCRPC and symptomatic bone mets followed by Ra-223. Pts received docetaxel in mCSPC were excluded. We evaluated the clinical outcomes of this population.

Results

From Jan 2020 to Jun 2023, 13 pts received Ra-223 as 2nd-line. Median follow-up was 15.7 mos (1.7-27.3). Median radiographic PFS was 6.5 mos and median OS was 10.2 mos. 7 pts had mediastinal or paraaortic lymph nodes (LNs) in CT scan before Ra-223. 10 pts had PSA progression during Ra-223 (6 of them had prominent LN and 4 could not complete 6 cycles due to lung and liver mets). 3 pts without LNs had stable PSA including 1 pt had PSA >30% reduction. The median calculated PSA doubling time (PSADT) was 5.6 mos (0.9-16) and PSADT < 3 mos passed away rapidly. For pts progression after Ra-223, they kept on ADT but no PSA response was found. 4 pts received docetaxel, enzalutamide or local RT as salvage therapies. One received oral cyclophosphamide as 4th-line after 3rd-line docetaxel and had a PSA reduction >50% and was still alive >12 mos without progression. The major adverse effect of Ra-223 was Gr. 3 anemia. 4 pts decreased opioid use after Ra-223. Table: 280P

Conclusions

Ra-223 use after first-line ABI/ENZ for mCRPC with bone mets should be cautious if pts had prominent LNs. PSA progression during or after Ra-223 leads to poor outcome and salvage therapy should be given earlier.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.