In theory, the high doses of testosterone will help the patient feel better and perhaps offset some of the symptoms of ADT (e.g., loss of libido, hot flashes, bone loss, lean muscle loss, mental symptoms).
In pilot trials so far, BAT was able to restore sensitivity to second-line hormone therapy, like Zytiga or Xtandi, in some men who had become resistant to their effects. If it can reverse castration resistance, can it also slow down the development of castration resistance?
Schweizer et al. report on 29 patients:
- None of the men in the study had started on androgen deprivation yet.
- None had symptoms.
- 10 had a low burden of metastases.
- 19 had no detectable metastases, but had recurrent disease after an attempt at a cure (i.e., their cancer was micrometastatic)
- They were all hormone sensitive. That means their PSA went down to less than 4 ng/ml after 6 months of ADT
They then received 3 months of testosterone injections, and then 3 months of ADT. Those cycles continued for a total of 18 months.
- They report that 17 men (59%) were still able to achieve their PSA goal (<4 ng/ml) at the end of 18 months. That is, they were still hormone sensitive.
- Of the 10 patients with detectable metastases at the start, metastases had shrunk completely in 4, and partially in 4. So 8 in 10 (80%) had a positive radiographic response to BAT.
- Six patients had metastatic progression.
- So, 13-15 of the 19 (68-79%) men with recurrent PC with no detectable metastases at the start still had no detectable metastases after 18 months of BAT.
- Evaluations of quality of life improved.
Another consideration is whether radiation ought to be included in the mix of early treatments. A few recent studies (see this link and this one) suggest that prostate radiation might still be beneficial to the metastatic patient. Moreover, a lab study suggests that radiation and BAT may be a particularly potent combination.
At this point, all of this is pure speculation. Future expanded clinical trials will have to determine whether BAT is useful for men with mHSPC, and what the optimal sequencing of therapies should be.