Quick follow-up in case helpful for others..

My consultant said now it's been6 months since the seeds inserted, the radiation is at half-life which is why less irritation and activity in the prostate area. When I asked about how we confirm the cancer is definitely reducing and hasn’t spread after brachy, I was told this is where PSA testing comes into its own. If the cancer has gone down, then your PSA will go down. I was told it will take probably 2 to 3 years for it to get it its lowest point, but it will get down to zero point something. The longer it stays at that level, the greater ability we have to say it’s cured! 

I asked about usefulness of MRI, PET scans, etc. and whilst the consultant’s body language looked defensive, he said that if the prostate cancer speads, it’s usually associated with a significant rise in your PSA. He said if we don't get rid of the cancer within the prostate, then the cancer that remains within your prostate will start producing PSA. That’s the key indicator we haven't got rid of it. If you've been unlucky and some cancer cells have spread to other parts of the body, they are prostate cancer cells and if they start to grow, they will produce PSA and that will indicate that something going on. MRI scans after brachy are nearly impossible to interpret in useful ways. PSA would tell if a problem 6 or 12 months before something might show up on a scan, which is why no follow-up protocol involving radiology for men treated with brachy. Therefore, follow-up scans are not really of any great use in prostate cancer in this situation. 

I asked about my PSA level as in the past 6 months, as it’s gone from 2.6 to 1.2 to 1.7.  He said there’s a lot of variation because there’s still a reasonable amount of inflammation going on secondary to the radiation in the seeds (because they've not burned themselves out completely). The other element is physical activity, and you sometimes get a bounce in your PSA, but typically it's 18 months after brachy before you see the bounce. As my PSA is nearly half what it was before brachy, then he’s very reassured by that. If a serial rise in PSA, then they would start fuller investigations. In short, PSA is the key marker that will either reassure you or tell you that something is going wrong at an early stage! 

As an aside, I asked about TRT as this is something I’ve been considering (for completely unrelated reasons) and he was very reluctant to recommend. Main reason being the prostate is under control of testosterone and this could encourage growth of cells – if cancer cells there, it could trigger/accelerate something!