Clinical characteristics and long-term outcomes of extreme responders to first line treatment of metastatic prostate cancer.

Abstract

266 Background: Contemporary trials show that the median overall survival of patients with metastatic prostate cancer is approximately four to five years. There is limited data on the clinical course and the long-term outcomes of patients who have lived beyond that (extreme responders). This study aimed to investigate the disease characteristics and treatment patterns of patients with long term survival following metastatic disease diagnosis. Methods: Retrospective, single-site study of 247 patients diagnosed with metastatic prostate cancer prior to Jan 1, 2019, and living as of Dec 31, 2024. We compared patients who did and did not develop castration resistant disease on first line therapy. Among those who did not progress on first line therapy, we examined treatment patterns of therapy cessation. Results: 247 patients were included. The mean age of the cohort was 62 years at diagnosis. The median follow up time for the cohort was 103 months (range 72-279 months). 154 (62%) had localized disease at diagnosis and 93 (38%) had metastatic disease at diagnosis. 140 (56%) had Gleason grade group 4 or 5; 121 (79%) of those with localized disease (n=154) were treated with prostatectomy as their primary therapy. 161 (65%) patients had bone only metastases; 45 (18%) had lymph node only metastases, and 25 (10%) had visceral involvement (alone or in combination with other sites). 101 (41%) of patients continued to have castration sensitive disease through a median follow up of 7.8 years. Among those patients, 26 (25.7%) stopped therapy prior to 12/31/2024, and of those, 21 had evidence of testosterone recovery, and 15 continued to have an undetectable PSA. This represents about 6% of our total cohort of patients who survived beyond 5 years and have no evidence of disease even with cessation of all prostate cancer directed therapies. Conclusions: Metastatic prostate cancer is thought to be incurable, however, there are some patients who have castration sensitive disease for long duration and a subset who can successfully stop therapy. Additional research is needed to further characterize clinical and biological parameters of patients likely to have long-term benefits from ADT to potentially stop treatment earlier, saving resources, and mitigating treatment-related adverse effects.