A PSA nadir of 0.1 ng/mL or higher within 6 months of completing radiation therapy (RT) plus androgen deprivation therapy (ADT) for localized prostate cancer strongly predicts worse oncologic outcomes and patient survival, according to data presented at the American Society of Clinical Oncology’s 2023 Annual Meeting in Chicago, Illinois.
The PSA nadir at 6 months after RT+ADT could be used as an early signal-seeking endpoint in trials evaluating novel systemic therapies with radiation therapy and androgen deprivation therapy, according to investigators.
Praful Ravi, MBBChir, of Dana-Farber Cancer Institute in Boston, Massachusetts, and colleagues analyzed data from 10,415 patients who participated in 16 randomized clinical trials. Of these, 2629 (25%) were randomly assigned to RT alone, 6033 (58%) to RT plus short-term ADT (3-6 months), and 1753 (17%) to RT plus long-term ADT (24-36 months). The median follow-up duration was 10.1 years.
“This comprises the largest assessment of the prognostic impact of PSA at 6 months after radiotherapy completion in patients receiving radiotherapy with or without ADT for localized prostate cancer,” Dr Ravi said.
The proportions of patients with a PSA nadir at 6 months of 0.1 ng/mL or higher were 98%, 84%, and 77% for patients assigned to RT alone, RT plus short-term ADT, and RT plus long-term ADT respectively. The proportions with a PSA nadir less than 0.1 ng/mL were 2%, 16%, and 23%, respectively.
The 10-year prostate cancer-specific mortality rates for patients with a PSA nadir of 0.1 ng/mL or higher were 14%, 15%, and 14% for the patients who received RT alone, RT plus short-term ADT, and RT plus long-term ADT, respectively. The rates for patients with a PSA nadir less than 0.1 ng/mL were 8%, 7%, and 7%, respectively.
The 5-year metastasis-free survival rates for patients with a PSA nadir of 0.1 ng/mL or higher were 79%, 76%, and 74%, respectively. For those with a nadir less than 0.1 ng/mL, the rates were 91%, 83%, and 87%, respectively.
The 10-year overall survival rates were 58%, 56%, and 50% for patients with a PSA nadir of 0.1 ng/mL or higher, respectively, compared with 52%, 62%, and 63%, respectively, for those with a PSA nadir less than 0.1 ng/mL.
The findings have potential implications for trial designs, Dr Ravi said. For example, it may be possible to use the PSA nadir thresholds to decide whether to intensify or de-intensify therapy, perhaps escalating therapy for patients with a PSA nadir of 0.1 ng/mL or higher and de-escalating therapy for those with a PSA nadir below 0.1 ng/mL.
Disclosure: This research was partly supported by Astellas, Pfizer, Janssen, Millenium, Sotio, Bayer, Dendreon, and Sanofi. Please see the original reference for a full list of disclosures.
Ravi P, Kwak L, Armstrong J, et al. Prognostic impact of PSA nadir (n) >0.1 ng/mL within 6 months (m) after completion of radiotherapy (RT) for localized prostate cancer (PCa): An individual patient-data (IPD) analysis of randomized trials from the ICECAP collaborative. Presented at: ASCO 2023 Annual Meeting, June 2-6, Chicago, Illinois. Presentation 5002.