Objective
At the first follow-up visit after salvage radiation therapy (SRT) for recurrent prostate cancer, which commonly occurs approximately 3 months following SRT, the only information physicians currently have to offer patients regarding likelihood of future biochemical outcome is based on pre-SRT characteristics. The aim of this preliminary study was to provide estimates of future biochemical outcome that are tailored to a given patient's PSA value at 3-month follow-up.
Methods
We identified 203 SRT patients who had a PSA measurement between 60–120 days following SRT completion (i.e., at 3-month follow-up). Patients were divided into two groups based on PSA at 3-month follow-up (<0.4 and ≥0.4 ng/ml). In the PSA <0.4 group, we estimated the future likelihood of biochemical recurrence (BCR) (PSA ≥0.4); in the PSA ≥0.4 group, we estimated the probability of future initial biochemical control (PSA <0.4).
Results
At 3-month follow-up, 134 patients had a PSA <0.4, and 69 had a PSA ≥0.4. In the PSA <0.4 group, cumulative incidences of BCR at 3 and 5 years after 3-month follow-up were 22 and 40 %; risk of BCR was highest in T3b tumor stage patients (Relative risk: 2.32, P = 0.005). In the PSA ≥0.4 group, cumulative incidences of initial biochemical control at 6 and 12 months after 3-month follow-up were 25 and 27 %; patients with a decreasing PSA at 3-month follow-up were 5.58 times more likely (P = 0.006) to experience initial biochemical control compared to other patients.
Conclusion
Our results allow physicians to have individualized discussions with patients regarding future likelihood of SRT response based on the 3-month follow-up PSA measurement; larger studies are warranted.