Since the approval of the second generation LHRH Therapies like Abiraterone acetate (Zytiga) plus prednisone (AA+P), many men we talk with at Cancer ABCs have been asking us if it is vital to continue taking first-line ADT (hormone therapy).
ADT, which causes castration, or the removal of androgens such as testosterone from the body, comes with many significant adverse side effects. These side effects include loss of libido, loss of bone mass, causing an increased risk of fractures, hot flashes, cardiovascular complications, metabolic complications like diabetes, etc. Given the host of ADT's potential complications, can stopping ADT improve the quality of life while not compromising the prostate cancer treatment?
In an abstract, 5046, presented at the 2019 Virtual ASCO Meeting, this question was asked. The abstract provided us with a summation from the SPARE-trial (NCT02077634); CH Ohlmann, C Ruessel, R Zillman, et al. asked what would happen if men with metastatic castrate resistant prostate cancer who were chemotherapy naive and who were taking Zytiga stopped first line ADT.
The SPARE-trial was an exploratory phase II study, including 67 men. In the trial, the subject men were randomized to receive continued ADT plus Zytiga and prednisone or Zytiga plus prednisone alone(without ADT) to determine the value of continuing ADT.
The researchers found that in all men who received Zytiga plus prednisone and ADT, their median testosterone levels remained below castrate levels throughout treatment.
In 18% of the men who only received Zytiga and prednisone (no ADT), their testosterone levels increased above castrate levels 28 days after treatment cessation.
They also found that the median treatment duration was shorter in the men receiving Zytiga plus prednisone and ADT.
The researchers concluded that ADT may not be necessary for men receiving Zytiga and prednisone; however, some men may experience a rapid increase of serum testosterone levels, warranting close monitoring and adding back ADT.
This research is not conclusive and only evaluated the possibility of halting ADT while taking Zytiga and prednisone. It did not evaluate stopping ADT with any other second-generation hormone manipulations like Xtandi or Darolutamide.
CAUTION
Under no circumstances should you stop your primary ADT treatment without a careful conversation and your medical oncologist's agreement. If you and your oncologist decide to stop ADT, you and your doctor must develop a cautious plan to AGGRESSIVELY AND CONTINUOUSLY monitor your serum testosterone levels.
