There is a new study out of Spain, which looked at a variety of long-term outcomes for 177 patients on ADT, who managed to have their testosterone (T) levels suppressed well below what is normally considered the cut-off for castration.
The traditional target for castrate levels of T has been <50 ng/dL. However, some recent papers suggest that it is better if the T level can be suppressed even further; i.e., down to or below 20 ng/dL.
This new paper by Zapatero and colleagues addressed two questions. The first is whether it really matters, in terms of disease progression or survival, if patients’ serum T level is <20 ng/dL when on ADT. The second question is whether it matters, in terms of disease progression or survival, if the T recovers slowly or quickly after ADT is stopped. Of note, the median follow-up time for the study was nine years.
The authors found that it did not matter whether the T was very low during ADT or recovered rapidly after stopping ADT. However, this is a small study involving only 177 patients. Moreover, other studies that have suggested “lower T is better” were looking at different populations with slightly different risk profiles for disease progression. Therefore, we still need more research involving larger samples of more diverse patients.
The paper does, in passing, address one other commonly asked question: How long does it take on average for the testosterone to recover after stopping ADT? This, of course, depends on the general health of the patient and how long they are on ADT, but in this study the average time turned out to be 16.3 months.
For patients who are on intermittent ADT in order to have breaks from the adverse effects of low T, they may be pleased to know that there is no particular risk associated with a rapid return to normal T levels when stopping ADT.
To read the full article, see: https://www.thegreenjournal.com/article/S0167-8140(21)06216-2/fulltext
Zapatero A, Álvarez A, Guerrero A, Maldonado X, González San Segundo C, Cabeza MA, Martín de Vidales C, Solé JM, Pedro Olivé A, Casas F, Boladeras A, Vázquez de la Torre ML, Vara S, Calvo FA. Prognostic value of testosterone castration levels following androgen deprivation and high-dose radiotherapy in localized prostate cancer: results from a phase iii trial. Radiother Oncol. 2021 May 5:S0167-8140(21)06216-2. doi: 10.1016/j.radonc.2021.04.018. Epub ahead of print. PMID: 33964325.
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