Would appreciate any feedback on my recent PSA results

Well its been 4 months since my Brachytherapy and had my PSA test yesterday. My PSA level dropped from 6.7 to 1.6. Doc seemed very pleased and I'm feeling good about things. He expects me to continue to do well but there is this side of me who is always wondering what is going on inside of me. I have had minimal side effects since the seeds (high dose) were planted. What do I need to concerned about? Anyone had a similar experience?
What should I be watching for? Thanks in advance for your feedback.

Take a deep breath, exhale and savor the moment.
None of us know what else may or may not be lurking inside, other cancers, heart disease, nothing, or what tomorrow will bring. Enjoy today.
All the best to you!

Newlife: Your stats are quite close to mine, including the quick drop in PSA. Your PC is being destroyed and your seeds are diminishing by half lives. Two good things, thus far, plus more PSA readings on the downward trend to come. Best wishes and keep us posted.

It's great to see a 6.7 PSA drop to 1.6 after the treatment you had. Congratulations!

But it brings to mind a nagging question of how do you track the effectiveness of the same treatment if you had started out with a PSA of 1.6 and Pca was diagnosed after a biopsy brought on by an abnormal DRE, not PSA. I'm not trying to "sell" any specific treatment. I'm just curious how easy it is to track the results afterwards. I gather you just hope PSA remains lower than the 1.6 that you may have started off with.