I did not have the seeds but did have IMRT. At the time my oncologist told me that anything under a 1.0 and steady was good results for radiation. The bounce, if it occurs, is usually between 18 and 24 months but can be as far out as three years according to some sources. One research paper indicated that post radiation nadir below .5 and two years to nadir had the best results for long term. Based on that I would say things look good for your husband.
As Geebra stated, and as my oncologist noted, there is still some viable prostate tissue after the treatment and it will express PSA.
Here's hoping for continued improvement and good health to your husband and you.
Diagnosed 04/10/08 Age 58 at the time
Gleason 4 + 3
DRE palpable tumor on left side
100% of 12 cores positive for PCa range 35% to 85%
Bone scan clear and chest x ray clear
CT scan shows potential lymph node involvement in pelvic region
Started Casodex on May 2 and stopped on June 1, 2008
Lupron injection on May 15 and every four months for next two years
Started IMRT/IGRT on July 10, 2008. 45 treatments scheduled
First 25 to be full pelvic for a total dose of 45 Gray to lymph nodes.
Last 20 to prostate only. Total dose to prostate 81 Gray.
Completed IMRT/IGRT 09/11/08.
PSA 02/08 21.5 at diagnosis
PSA 07/08 .82 after 8 wks of hormones
PSA 10/08 .642 one month after completion of IMRT, 6 months hormone
PSA 03/09 .38 six months post radiation and nine months into hormones