Intermittent androgen suppression in prostate cancer: an update of the Vancouver experience.
BACKGROUND
This report will review the long-term follow-up of a prospective Phase II evaluation of intermittent androgen suppression in the treatment of prostate cancer. Specifically, this analysis will address completed cycle characteristics, the concept of prolonged off-treatment cycles, the time to cancer progression, cancer-specific survival and the association between PSA and bone scan changes.


METHODS
A total of 102 patients have been entered into this protocol. Treatment was initiated with combined androgen blockade and continued for 6 months or longer to reach a serum PSA nadir. Medication was then withheld until the serum PSA increased to predetermined trigger points based on initial parameters. Each cycle of treatment and no-treatment was repeated until the regulation of PSA became biochemically androgen independent.


RESULTS
One hundred two patients have been commenced on IAS with an average follow-up time of 219 weeks (range: 14.5 to 588). Ninety-one patients have completed at least one therapeutic cycle with a total of 188 completed cycles available for analysis. The average time off therapy (percentage time off therapy) for cycles 1, 2, 3 and 4 was 13 months (53%), 11 months (51%), 10 months (47%) and 8 months (45%), respectively. A prolonged off-treatment time of greater than 72 weeks was observed in 33 (18%) of all completed cycles, and was most common in the men being treated for radiation failure stage C. Progression and survival data was calculated for the entire trial cohort (n=102). The average time to androgen independent progression in the 29 (28%) patients who progressed was 194 weeks. Death from prostate cancer occurred in 19 (18%) patients at an average of 258 weeks following treatment initiation. A review of bone scans revealed 22 events of newly detected lesions, all but 2 of which were preceded by a rise in serum PSA.


CONCLUSIONS
Longer duration follow-up of a single cohort continues to support IAS as a viable treatment option for men with prostate cancer. This approach affords an improved quality of life when the patient is off therapy, with reduced toxicity and costs. There is a trend toward extended times to progression and death compared to contemporary studies of continuous androgen suppression. Randomized, prospective protocols are currently underway to determine whether survival is affected in a beneficial or adverse way in men with locally recurrent or metastatic cancer.
Pether
Michael
M
The Prostate Centre at Vancouver General Hospital, Division of Urology, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada.
Goldenberg
S Larry
SL
Bhagirath
Kapil
K
Gleave
Martin
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000726:Androgen Antagonists / Q000627:therapeutic use*; D001859:Bone Neoplasms / Q000556:secondary; D017322:Clinical Trials, Phase II as Topic; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D016896:Treatment Outcome
D000726:Androgen Antagonists; D017430:Prostate-Specific Antigen