The impact of salvage radiotherapy initiation at PSA ≤ 0.5 ng/ml on metastasis-free survival in patients with relapsed prostate cancer following prostatectomy
Abstract
Background and Purpose
Salvage radiation therapy (SRT) is indicated for biochemical failure after radical prostatectomy. Prior data have shown that initiation of SRT at lower PSA levels improves subsequent biochemical control, yet given the long natural history of prostate cancer questions remain regarding optimal timing of SRT. We analyzed the impact of prostate specific antigen (PSA) level at time of salvage radiotherapy with regard to both biochemical relapse-free (bRFS) as well as metastasis-free survival (MFS) in patients with biochemically recurrent prostate cancer.
Methods
Using prospective institutional tumor registry data, univariate and multivariable-adjusted Cox proportional hazards models were constructed to assess association between outcomes and clinical and pathologic prognostic features, including pre-SRT PSA, interval from prostatectomy to SRT, androgen deprivation therapy (ADT), and adverse pathologic features.
Results
We identified 397 patients who received salvage RT between 1985 and 2016: 187 (45.8%) received SRT initiated when pre-RT PSA was ≤0.5 ng/ml; 212 (52.0%) patients had pre-SRT PSA > 0.5 ng/ml. Independent of pathologic risk status and ADT use, pre-SRT PSA ≤ 0.5 ng/ml was the most significant predictor of bRFS (HR 0.39, 95% CI [0.27, 0.56]) as well as MFS (HR = 0.58, 95% CI [0.37, 0.91]). Seminal vesicle invasion was also associated with shorter interval to biochemical failure, HR = 1.79, 95% CI [1.07, 2.98], and eventual metastases, HR = 2.07, 95% CI [1.14, 3.740].
Conclusions
Initiation of salvage RT while PSA levels remain ≤0.5 ng/ml was associated with improved MFS. Consideration for salvage RT initiation while PSA levels remain low is warranted to minimize risk of future prostate cancer metastasis.
CONFLICT OF INTEREST
Phuoc Tran (PTT) is a consultant for Janssen-Taris Biomedical and RefleXion, Personal fees from Noxopharm, Janssen-Taris Biomedical, Myovant and AstraZeneca; Holds a patent 9114158- Compounds and Methods of Use in Ablative Radiotherapy licensed to Natsar Pharm. PTT was funded by an anonymous donor, Movember Foundation-Distinguished Gentlemen's Ride-Prostate Cancer Foundation, Babara's Fund, National Capitol Cancer Research Fund and the NIH/NCI (U01CA212007 and U01CA231776) and DoD (W81XWH-21-1-0296). The remaining authors declare no conflict of interest.
Open Research
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
