Metasatic prostae cancer with no evidence of recurrence on or after ystemic treatmetn is more and more commonluy seen in clincal practice. There are no studies supporting routine imaging. NCCN(MS-16) recommends that clinical monitoring is determined by intensity of response to intial androgen deprivation, radiation or both. It mentions history and exam, digital rectal exam and PSA every 6 months. It does not recommend imaging.
nccn.org, prostate cancer
A. Horwich, C. Parker1, C. Bangma2, V. Kataja and On behalf of the ESMO Prostate cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
Ann Oncol (2010) 21 (suppl 5): v129-v133.