I just want to make sure that this comment is clarified, because it is not at all true:

" ...but I am also reading that early BCR with doubling rates < 6 months puts 5 year survival at < 20%. "

This would be more accurate:

Research has shown that while a short PSADT is a negative prognostic factor, the 5-year survival rate is not as low as the statement suggests. Several studies have shown that for patients with BCR and a short PSADT, the risk is more focused on the development of distant metastases and a shorter time to death from prostate cancer, rather than a low 5-year overall survival. A large-scale analysis of men with BCR after prostatectomy found that those with a short PSADT had a significantly increased risk of developing distant metastases, but the 5-year metastasis-free survival was still well over 50%.
Additionally, the overall cancer-specific survival for men with biochemical recurrence is generally quite high, with some studies reporting 10-year cancer-specific survival rates of over 90% after salvage therapies like radiation. This shows that even with a high-risk feature like a short PSADT, many patients can still have a good prognosis due to effective follow-up treatments.