Optimal definition of BCR after SRT following RP

Optimal Definition of Biochemical Recurrence in Patients Who Receive Salvage Radiotherapy Following Radical Prostatectomy for Prostate Cancer (2021)

"Abstract

Purpose: This study proposed the optimal definition of biochemical recurrence (BCR) after salvage radiotherapy (SRT) following radical prostatectomy for prostate cancer.

Materials and methods: Among 1,117 patients who had received SRT, data from 205 hormone-naïve patients who experienced post-SRT prostate-specific antigen (PSA) elevation were included in a multi-institutional database. The primary endpoint was to determine the PSA parameters predictive of distant metastasis (DM). Absolute serum PSA levels and the prostate-specific antigen doubling time (PSA-DT) were adopted as PSA parameters.

Results: When BCR was defined based on serum PSA levels ranging from 0.4 ng/mL to nadir+2.0 ng/mL, the 5-year probability of DM was 27.6%-33.7%. The difference in the 5-year probability of DM became significant when BCR was defined as a serum PSA level of 0.8 ng/ml or higher (1.0-2.0 ng/mL). Application of a serum PSA level of ≥ 0.8 ng/mL yielded a c-index value of 0.589. When BCR was defined based on the PSA-DT, the 5-year probability was 22.7%-39.4%. The difference was significant when BCR was defined as a PSA-DT ≤ 3 months and ≤6 months. Application of a PSA-DT ≤ 6 months yielded the highest c-index (0.660). These two parameters complemented each other; for patients meeting both PSA parameters, the probability of DM was 39.5%-44.5%; for those not meeting either parameter, the probability was 0.0%-3.1%.

Conclusion: A serum PSA level > 0.8 ng/mL was a reasonable threshold for the definition of BCR after SRT. In addition, a PSA-DT ≤ 6 months was significantly predictive of subsequent DM, and combined application of both parameters enhanced predictability."

Djin

Thanks for this Djin, its something i relate to. Being only 2 1/2 years out of SRT+ADT, I am always aware that this fight may not be over for me, hopefully that is not the case. As you may recall, my RO at MSK has me test at MSK lab, which has a threshold for detectable of .05. So while i wonder sometimes if i am becoming detectable below the .05 mark, knowing that there are studies showing that .08 is a reasonable cutoff, makes me a bit more comfortable.
I'd think others treated for salvage at MSK would feel this way as well

Not clear to me what authors' point is. I think many MOs would initiate palliative treatment when a clear PSA trend presents with a short doubling time. Are they suggesting that a PSA above 0.8 is also a trigger for palliative treatment?

I'm not seeing what they feel is the significance for their predictions of DMs. If your PSA is steadily increasing after "curative" treatments, then you have mets (or there is still cancer in the prostate bed). Maybe their predictions could somehow help with identifying DMs for radiation?

Am I missing something?